A while ago, I wrote a blog about the error message ‘Application can’t be started… (Instant Passthru could not be resolved)’ that we encountered when launching a published application from our Ivanti Workspace Control managed session. Recently, we received the same message again, but this time the cause was different.

Application can’t be started… (Instant Passthru could not be resolved)

Shortly after a relatively simple task—upgrading an outdated version of Citrix Workspace App (CWA) from 1912 LTSR to the slightly newer 2203 LTSR—we encountered some inexplicable issues that made it impossible to launch Citrix Published Apps via SelfService.exe.

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Apple OSX users sometimes experience an incorrect keyboard layout loaded within their Citrix session. As a result, special characters are often located in different places. The cause of this issue is that Apple has a different keyboard layout compared to Windows, leading to an Apple US-international keyboard being recognized as a Dutch keyboard in Windows.

How to identify your Apple keyboard layout by country or region

Some time ago, we conducted extensive research together with Citrix Support to investigate the cause of this issue and whether there are possibilities to change this behavior. Unfortunately, it has been found that this behavior cannot be changed through a central solution. This behavior can only be altered by making adjustments on a per OSX system basis. This guide provides detailed instructions on what needs to be adjusted.

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We manage a Citrix farm where users primarily launch a full desktop environment. From there, they can also connect to other applications running in Citrix Silo’s or access external Citrix farms. As an user environment manager (UEM), we utilize Ivanti Workspace Control (IWC).

When a user logs onto the primary desktop, the endpoint hostname is utilized by Ivanti Workspace Control within that session. Based on the endpoint hostname, we can set specific configurations using features like “location and devices”. In a double-hop scenario, where a user launches a Citrix published application or another Citrix desktop from within the primary session, the hostname of the primary session server is used as the hostname in the secondary session.

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Due to lifecycle management (LCM), we replaced several Citrix NetScaler appliances with new ones. Although we conducted thorough acceptance tests before putting them into production, unfortunately, we experienced an annoying issue once they were operational.

Some users complained that they saw a spinning progress bar after they successfully logged on to the Citrix NetScaler. It was only reported by a minority of users and was resolved by refreshing their web browser sessions. In the end, users stopped reporting the issue because it occurred infrequently and the solution was simple—just press F5. We initiated an investigation in the hope of completely resolving the issue.

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A “security.txt” file is a standard proposed by security researcher Ed Foudil in 2017 as a way for websites to define a security policy. It’s akin to the well-known “robots.txt” file which specifies rules for web crawlers. The security.txt file allows website owners to provide information to security researchers about how to report security vulnerabilities or concerns.

Since April 2022, Security.txt has been an Internet Engineering Task Force (IETF) informational standard

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Recently, we worked on upgrading a Citrix NetScaler VPX from version 13.0 to the latest 14.1 build. The Citrix NetScaler VPX, which had been running for quite some time, had not been upgraded because it still used features and functionalities, including Classic Policies, which essentially needed to be replaced by Advanced Policies starting from the 13.1 build.

During the preparation for the upgrade, our main focus was on the legacy configuration in the running ns.conf file that needed to be adjusted.

Citrix ADC scripts for migrating and converting Citrix ADC configuration with deprecated features https://github.com/netscaler/ADC-scripts/tree/master

By using the NSPEPI tool, you can not only check for legacy configuration but also convert it to new configurations in many cases. Always ensure that you download and use the latest version during the analysis. If you are upgrading from a version older than build 13.1, always use NSPEPI beforehand to ensure that everything continues to work as expected after the upgrade.

check_invalid_config /nsconfig/ns.conf

After replacing all legacy configurations in the ns.conf and ensuring there were no blocking issues according to the NSPEPI tool to upgrade to the latest 14.1 build, we conducted a trial upgrade migration within our acceptance environment.

After the upgrade, the Citrix NetScaler restarted smoothly, but it was no longer possible to log in using our domain accounts (LDAPS). Fortunately, logging in with the local nsroot account still worked. Once logged in, it was immediately apparent that several load-balanced VIPs were down, causing the LDAPS load balancer to be inactive. Additionally, various NetScaler features were suddenly no longer visible.

Show Unlicensed Features

The navigation suddenly included an item labeled “Show Unlicensed Features,” which we hadn’t seen before. After clicking on it, all features became visible again. However, it became immediately apparent that many things seemed to be unlicensed all of a sudden. Features that we were using prior to the upgrade to build 14.1. While browsing through the NetScaler GUI, we navigated to System > License and discovered that we were running an Express edition instead of Platinum. Consequently, many of the commonly used features were indeed unlicensed.

ADC License

Next, we examined the existing license files located in the directory /nsconfig/license. What immediately caught our attention was the date present in the license file. In our case, the expiration date was older than the Eligibility Dates required for using the Citrix NetScaler 14.1 build, which is July 12, 2023 🙁

NetScaler License File

Citrix products and their Eligibility dates https://support.citrix.com/article/CTX111618/citrix-product-customer-success-services-eligibility-dates

Since this was a Citrix NetScaler VPX with a valid software subscription, the solution was fortunately quite simple. Simply redownload your license file via the MyCitrix license portal and upload it to the Citrix NetScaler VPX. The new license file will include a new SA Date, enabling you to run build 14.1. After restarting the Citrix NetScaler, all previously licensed features reappeared.

Check your product eligibility dates before you proceed with the upgrade!

In the past, it was possible to upload your NetScaler configuration file (ns.conf) to the Citrix Insight Service, which would then conduct an automated health check of the configuration. You would receive a report detailing any potential issues, best practices not followed, and so on. This was incredibly helpful during setup. Unfortunately, Citrix discontinued this self-diagnostic service some time ago.

During E2EVC 2022 Athens, I stumbled upon the “Arrow’s NetScaler config analyser” in one of the sessions—a tool more than handy. After registration, it allows you to check your NetScaler configuration for free. However, in practice, I still regularly encounter NetScaler administrators who are unaware of its existence, so I thought I’d mention it again.

Arrow’s NetScaler config analyser https://app.xconfig.io

Although they offer more than just the free health check, in this case, I want to specifically mention the FREE “Online Config Analysis.”

Unless you choose to save your ns.config within your personal account, your ns.config is not uploaded to their website; instead, it is analyzed locally from your browser session.

For added security, it’s advisable to first mask any confidential data such as passwords, IP addresses, etc., ensuring they’re not usable.

Without registration, not all results are visible, so go ahead and register yourself.

After creating an account, you’ll have full visibility into all the issues discovered within your ns.conf. These issues are categorized into four categories:

  • Critical
  • Major
  • Medium
  • Low

If you ask me, your configuration shouldn’t contain any Critical, Major, or Medium findings! 😊

An example of a Critical finding might be:

An example of a Medium finding might be:

What’s also very handy besides the analysis of your NetScaler configuration is the easy browsing through your configuration. By selecting an item on the left side (which looks identical in structure to a NetScaler), you’ll see the corresponding lines from your configuration on the right. This makes the configuration much more readable and understandable.

The tool is constantly evolving, with new recommendations being added regularly. For a comprehensive overview of the change log, you can navigate to the “What’s new” section. If you encounter false positives or have recommendations for improvements, don’t hesitate to let them know. In my experience, they are responsive to user feedback and often address issues or implement suggestions in subsequent releases!

Recently, I worked on a project where the workload needed to shift from using a Citrix Published Desktop to a physical laptop, with locally installed applications. As always, there are applications that, for various reasons, cannot be moved from the Citrix Published Desktop to the physical laptop. For these applications, we chose to offer them as Citrix Published Applications. Although this transition went well technically, end users reported that working with published applications was not considered very pleasant.

Scenario: The published apps were offered from a Citrix Virtual Apps en Desktops Farm, utilizing Ivanti Workspace Control. Ivanti Workspace Control is a workspace management solution provided by Ivanti, a company specializing in IT management software. It offers features for managing user workspaces across various devices and environments, including physical desktops, virtual desktop infrastructure (VDI), and application virtualization platforms. Unfortunately, Ivanti has announced that Ivanti Workspace Control will reach end of life on December 31, 2026, but at the moment, we are using it to our full satisfaction. When starting a Citrix Published Application, it takes some time due to, among other factors, the loading of the Windows profile and Ivanti Workspace Control settings before the application actually starts. When you subsequently start a second published application, it loads faster since the entire profile and UEM (User Environment Management) don’t need to be processed again. When you close the last Citrix Published Application, it also logs out the entire user session, resulting in the next Citrix Published application taking some time again, as your entire Citrix sessions needs to be loaded

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Last Monday, we started getting multiple reports from MacBook users experiencing an issue with their Citrix Workspace app for Mac. At first the issue wasn’t very clear to use, because everybody reported it slightly different, but soon we noticed the common thread was the resolution. Affected users somehow got a very high resolution in their Citrix session, while their local screen resolution was normal. The Citrix session didn’t seem to adopt the local screen resolution.

I wasn’t able to reproduce the issue myself, so I contacted an affected user. He had done some analyses himself and discovered a curious phenomenon. If you would ran the Citrix Workspace App setup again all seemed to be fine. A Citrix session would adopt the local screen resolution upon connection. Soon as you rebooted the MacBook, the problem suddenly returned. Reinstalling the Citrix Workspace app again made the issue disappear.

We compared the Citrix Workspace App version we were both using and noticed a small difference. The affected user was running version 22.04.0.44, I was running 22.04.0.25. By the end of the day I upgraded my Citrix Workspace App to version 22.04.0.44 and rebooted my MacBook hoping I would also be able to reproduce the issue. And indeed I had the issue myself 🙂

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An external software supplier wanted to make a new app available for a selected group of smartphones. We were asked if it would be possible to retrieve the smartphone from the XenMobile database. New smartphones added to the delivery group would be detected automatically. Since XenMobile has a REST API, this didn’t seem like a problem at first. We made the REST API available to our software supplier, after which they created a link between their backend and our On-Prem XenMobile environment based on the Citrix XenMobile REST API documentation

Public API for REST Services

At first everything seemed to work perfectly and our software supplier thought they saw all our devices. After some time we noticed that there was a difference between the devices visible in the XenMobile console (Web GUI) and the devices that our software supplier saw through the REST API. Based on the query that was used in the REST API, we then did some testing ourselves using Postman, in the hope of uncovering the difference in devices.

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