Quote I'm running the latest version of PowerDVD 21 Ultra and close button will not exit the application, it does nothing. I am forced to kill the process in task manager. This happens every time I use the program. This has never happened to me before in any previous version.

You may try uninstalling powerdvd and discard all personal settings.
Reinstall the new powerdvd version again, and not to import any previous version settings when you launched it first time.

It might resolve some weird issues that occur after you carried the previous settings to the new version directly.

or, you can contact cyberlink support to investigate this matter,

This was a fresh install. In fact it was fresh with a fresh windows 10 install too because I had built a new system at the time.