I've encounter the same issues. I have a custom app that read the variables and stores them in a database for auditing reasons. How quickly are you checking the variables? Those do not get set right away and can take some time before they are created in the registry. I've seen up to 2 minutes if at all. Based on my experience I don't suggest relying on those variables. I don't have an alternate suggestion for you. I do know UEM can see that same type of information and you can base conditions around that but I don't think that would apply to your use case.
We have been using the ViewClient_Mac_Address variable for a few years without issue. The ViewClient_Mac_Address variable is used in the Target Path of an Application Shortcut. And because it cannot be located the application fails to load.
Thanks for letting me know that there can be up to a 2min delay before they get created. I'll ask some users to wait 2-5min when they experience the issue and see if it works after that.
It's just strange as it is an issue that has only occurred recently and is intermittent
waiting 2-5min didnt make a difference, unfortunately
What are your clients? I've seen a similar issue with our Wyse Thin OS clients. Turned out that the ThinOS firmware version was to blame. If I remember correctly I had a beta firmware version on my test terminal at that time. When we upgraded the firmware it started working again.
We are mainly using WYSE Thinclients, however the issue is also impacting some user's that are just connecting from home, from their laptops or desktops. So it does not appear to be only restricted to WYSE Thinclinets
Have you reinstalled the Horizon Agent on the parent/gold image and rebuilt the VMs? Have you reverted to the last known good version of the Horizon Agent or tried another agent?