Hello Paul,
Sorry for keep you waiting so long. May I confirm with you whether this’s class note created in OneNote Class Notebook and then being connected to Teams? If so, you may try to re-connect it. If this way doesn’t work either, or this class note is the default tab and was initiated in Teams, we tried to analyze the logs but couldn’t find related cause, as subsequent troubleshooting requires network debug log, we will send you a PM (private message) to summarize your issue and all the troubleshooting we have done according to our new policy.
Best Regards,
Anna