Remote support (i.e. remotely seeing UAC prompts) working for some but not all users

I have had mixed success with remote support for my approximately 35 users. 

The 64-bit Zoom MSI was deployed to them via a GPO.   (This causes Zoom to install when the computer boots up).

I can remotely see UAC prompts on some people's computers but not others.   

Note that most users already had a 32-bit per-user version of Zoom installed.    With this version you can remotely control screens, but if anything requires elevation (e.g. installing or uninstalling something), you don't see the UAC prompt.   

When both versions are installed, you don't see the UAC prompts.   

The problem seems to clear up for some users, but not others, when the 32-bit Zoom is removed.