I have noticed several times when I attempt to start Emby Theater it will appear that nothing has happened. There is no splash screen or any other indication that I actually launched the program. So I will often double click again and again, trying to get the program to launch.
After this happened to me several times over a period of time it became evident that Emby Theater was actually downloading and installing an update to itself. On a desktop machine the update process would usually complete within a minute, so I got used to just waiting for a couple of minutes if Emby Theater did not appear to launch immediately. However, I have two Windows-based tablets I use (a Dell and an off-brand) and they are generally slower than most desktops so it takes a much longer time to update and install. The first time it happened I again clicked on the Emby icon and Windows told me there was no such program and offered to delete the shortcut!
Anyway, I understand what is happening and what I wanted to suggest is that when Emby updates itself at startup that it would put up a splash screen letting the user know that an update is in progress. This splash screen should stay up during the update process and then go away when the update is finished and Emby Theater actually starts. This would let the user know that Emby Theater actually launched, but the program is busy updating itself.