Notes app on MacBook not accepting the correct password.
On my MacBook Pro (Retina, 15-inch, Mid 2015) running macOS Big Sur 11.1 (20C69), I was unable to unlock notes using my Notes password. I know the Notes password, and I'm sure I do, because I was able to type it in on my iPhone in order to unlock the same iCloud note on the same Apple ID. I typed it at least 20 times on my MacBook just being absolutely sure I wasn't mistyping it, which I wasn't, but it wouldn't unlock. I realized it just wasn't accepting the correct password.
There is an option to reset your Notes password, but this reset only allows you to create a new password for notes you lock from now on. Notes that already have a password aren’t affected. So after the reset, I was still unable to unlock my notes.