I'm unable to open a new or existing file, nor am I able to open the preference, or any other available command. I've attempted to completely remove and uninstall, and then reinstall both Creative Cloud and Adobe Photoshop 2021 multiple times and I am still having issues. I am able to use other CC programs, but Photoshop gives me an error each time.
We'll need some specifics - OS version, HD space available, RAM, Video/Graphics Card(s), VRAM, specific PS version.
Have you tried starting up with the reset preferences command? Hold Shift+Ctrl+Alt (win) or Shift+Ctrl+Cmd+Opt (mac) prior to the splash screen appearing. It should ask if you want to reset your preferences.
Adobe Community Professional/Adobe Certified Instructor