I can't uninstall elements 2021....something is missing....I want to reinstall it.

What OS - Mac or Windows?

what is the problem you are trying to correct?

How are you trying to uninstall?  What is the exact error message you are getting when you make the attempt.?

If you are on Windows, you can try installing over the current installation. That should replace any missing uninstall files. You may then be able to uninstall and reinstall again if that is really what you want to do.