Notes app won't open in Catalina

Hello amdgpu,

Thanks for that info and for choosing the Apple Support Communities. If I understand correctly, you are unable to open the Notes app on your Mac, as you get an error. You can figure out if unexpected behavior is related to a user file or setting by trying to reproduce the issue from another user account. This process includes creating a new user account, logging in to it, and testing for the issue.

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

Next, use safe mode to start up your Mac as it does the following things:

• Verifies your startup disk and attempts to repair directory issues, if needed
• Loads only required kernel extensions
• Prevents Startup Items and Login Items from opening automatically
• Disables user-installed fonts
• Deletes font caches, kernel cache, and other system cache files

Log in to your user account and test the issue while in safe mode and then restart normally and test the issue again.

Use safe mode to isolate issues with your Mac

Graphics performance limited in macOS Recovery, safe mode, or Guest User mode

Cheers!

Thanks for replying, amdgpu, and that additional info, it really helps! Next, try running First Aid on your hard drive with the built in Disk Utility tool, as this can correct simple issues like you're experiencing.

Disk Utility for Mac: Repair a disk using Disk Utility

If you're still having this issue, you can make a backup of your personal data and put a fresh copy of macOS on your Mac using macOS Recovery mode, as that will overwrite these system files causing the issue.

Back up your files with Time Machine

How to back up your Mac - Official Apple Support

How to reinstall macOS

Have a great day and thanks for using the Apple Support Communities!