I'm only adding this because I searched on here & all over the net for a solution but the options were vague & very varied.

I was opening Mocha Pro standalone from the Start menu or the Taskbar icon ok after a PC restart, but once Vegas was opened Mocha Pro standalone then only opened as a Background process 😒 Only a PC restart would fix this, it would then open but opening Vegas again would make it return to just opening as a Background 😒

I went through a whole list of things, uninstalling / reinstalling, restoring the PC etc. That list is in this Boris forum post https://forum.borisfx.com/t/mocha-standalone-not-loading-ui/17640/10

Uninstalling things inc removing Vegas 21 (187), this didn't fix the problem even though it seemed to be causing it 🤷‍♂️ So i reinstalled Vegas.

Near the beginning I'd tried reinstalling the Nvidia Studio driver 546.01 & even tried installing the Gaming driver without any luck.

Finally I decided to reinstall the last Studio driver 537.58 (I think it was the one before 546.01)

YAY, so far it seems fixed, Mocha Pro opens every time now.

I was going to try this near the beginning of my adventure but I've never had a problem with GPU drivers before & after trying the Gaming driver I moved on to trying other things,

Like I say I'm just posting this for the sake of sharing & so it's in here to find if needed.