Parallels 15 for Mac with Catalina is UNSTABLE, FREEZES, SHUTS DOWN, DOESN'T LAUNCH, etc.

Hello. I'm almost at the end of my rope when it comes to Parallels 15 for Mac.
I paid a fair bit of money for this software, but it is completely unreliable.
Here are just some of the issues I encounter:
1) I try to open an app in Windows/Parallels. It says it's opening but never opens.
2) I close and reopen Parallels, but nothing happens. It JUST WON'T OPEN.
3) It will finally open but totally randomly. It's not after I type or click something right. It just starts working (and not working).
I really need Parallels to work properly in order for me to incorporate it into my workflow. But ever since Mac Catalina (and Parallels 15) it has become all but unusable.
Can somebody please tell me, in plain, easy-to-understand English, how to fix this?
Thank you.

 

Hi, please try instructions from this KB article and let us know if it's not that case.