I have many messages on the Transaction screen in the app saying "There are multiple notifications from your banks". However I no longer have those bank accounts!

Hello Icab, 

Welcome to the Community page, 

Have you tried uninstalling the app and reinstalling it again and see if them messages and accounts go away for you if you no longer have them in your account. 

I have uninstalled and re-installed numerous times. I have no issues when using the web interface, just the mobile app which refuses to let me clear the very old notifications.