Hi ipodtrip,
Thanks for your update.
Since the Office 365 account works well both in Outlook Web App (OWA) and other Windows computers, it indicates that this account works well from the server side. In this situation, you can refer to Ran’s suggestion to set up the Office 365 account in another workable Mac to check if the issue persists. If the issue doesn’t exist, you can try create a new profile on your Macbook Proto see if there is any improvement.
Any updates will be appreciated.
Best Regards,
Anna