I just completed an upgrade from Citrix Workspace Environment Manager 4.04 to 1906. The upgrade was relatively smooth. However, I did run into a couple of unexpected issues:
When trying to launch and connect via my upgraded Console, I received: Error while connecting to the specified Infrastructure Server!
I checked the service on my WEM Servers and sure enough, wouldn't ya know it! The service was now set to Manual and set to run as Local System. My previous settings with my service account did not persist. Putting the service settings back the way they should have been, resolved the problem.
Interestingly, 1906 is the first release that should not require re-setting things during the install. After upgrading, when you choose save in the Configuration Utility it SHOULD set the service back to the way it was before upgrade but it did not in my instance, thus doing it manually.
2.) Agent Upgrade Failed
This one was much worse and more time consuming. I had multiple images to update with the 1906 Agent. All but one upgraded just fine.
The one that did not upgrade, seemed to try to look for copy of the full MSI for the old version of WEM. I tried to use the Uninstall string provided in the reg but it didn't help, same issue. I tried to find the cached MSI as seen in the above screenshot but that also did not work. In the end, I had to go extract the full WEM Agent MSI from the installer of the older version and then put it in a local directory on the server and point to that in the above dialog. That allowed the old version to uninstall successfully and make way for the upgrade.
Hopefully nobody else runs into these issues but if you do, I hope this helps you resolve them!
Other than these issues, the upgrade was smooth.