my screenshots won't open

Hello Brendon001,

Thank you for using Apple Support Communities! I understand that you're unable to view screenshots on your mac after upgrading to macOS Catalina. You've come to the right place for help.

To help further isolate potential causes for this behavior, I suggest seeing if this continues to be an issue when you restart your Mac in safe mode:

Use safe mode to isolate issues with your Mac 

If you're able to view screenshots, the next step would be to rule out incompatible login items:

If your Mac has a blue screen or other startup problems

Specifically, check out the section labeled “Test your login items”

Also, testing in another user account can also help determine if this may be user or account related settings causing this issue. If you don't have another user account, here's how you can create one for testing:

How to test an issue in another user account on your Mac

Best Regards.