Contacted AppleCare yesterday - informed them that I received my coverage email, and when I go to the checkcoverage website all is fine - but phone still shows the banner in settings.
He went away for a while, did his check, then came back to assure me everything was fine and that I was covered, so I can go ahead and ignore the banner. Hopefully it will update after a few days.
Personally I don't think he understood what I was trying to explain..... 🤦♂️