While attempting to upgrade a Windows Server 2016 VDA from XenDesktop 7.15 to 7.15 Cumulative Update 1, you may receive the error “Installation of the ICA for Remote Desktop Services failed with error code 1603.”.
Digging through the log indicates the issue is during the installation of the IcaTS_x64.msi component.
Running that installer directly indicates a possible permissions issue with the registry key “HKLM\SOFTWARE\WOW6432Node\Citrix\Euem\LoggedEvent”. The error displayed is “Could no open key: HKEY_LOCAL_MACHINE32\SOFTWARE\Citrix\EUEM\LoggedEvents. Verify that you have sufficient access to that key, or contact your support personnel.”.
The registry key does not have permissions/owners set, which is the problem. You will need to take ownership of the key, I set it to the local Administrators, and then inherit permissions to the key while replacing on any object below it.
After setting the permissions on the registry key, run through the installation again to successfully upgrade the VDA.
Thanks for reading!