Notes won't open in Sequoia

Did safe mode help?

If not, you might try to disable/enable Notes in iCloud settings (backup before doing anything):

If that does not help, you might try to re-create Notes preference file:

Choose Finder > Go > Go to Folder..., paste the following line, and press the Return key (*):

~/Library/Containers/com.apple.Notes/Data/Library/Preferences/

There should be "com.apple.Notes.plist" -- move it to the Desktop. Reboot the Mac and open Notes. If it then works, trash that old "com.apple.Notes.plist" from the Desktop.

Some setups might have the file in the following folder so you might try that:

~/Library/Preferences/

(*) Another way to find that preference file is to Option-click Finder > Go > click Library. Then open Containers. There are three (sic!) Notes folders, open the topmost (make sure you are sorting as List A to Z) and open Data > Library > Preferences.

Try booting into safemode and test to see if Notes is working there. Then boot back to normal and try it.

Start up your Mac in safe mode - Apple Support