Yesterday I installed Parallels Desktop 16 Pro on macOS Catalina 10.15.6 and Parallels Desktop 16 crashes right after Windows starts. I have Windows 10 Pro version, latest build, perfectly update and very stable in Parallels Desktop 15 Pro.
I've tried installing PD 16 several times, clearing preferences, etc. with the same bad result.
Important! Note that even if PD 16 crashes, it still remains active in background and visible in the Activity Monitor and to reinstall or reinstall PD 15 it must first be forced to quit from here!
[I am an experienced Mac user and have known and used Parallels Desktop since the earliest versions.]