error message to change Apple ID password keeps popping up but I DID change it

Over the weekend I changed my primary email address everywhere. The most ridiculous experience has been with my Apple ID. It was so confusing I don't even know how to explain what happened. I finally succeeded but I keep getting this stupid notification every time I log into my iMac. My iPhone was also asking me to sign in with my OLD Apple ID for a few days too, until I decided to try signing out again and thought of signing out of iTunes too -- on my PHONE -- and then log back in again. Now my phone is acting normally again. But doing the same thing on my iMac - signing out and then back in for both iCloud and iTunes -- hasn't made the stupid notification pop up stop.

Does this make sense to anyone? Can you tell me what else I need to do? I am definitely logged in with my new email address and my notes and contacts are synching fine between my phone and iMac. It's just this annoying pop up on my computer I don't understand and want to be rid of.

Thank you!