I'm trying to build a flow, and the connector gives this error message: "REST API is not yet supported for this mailbox." This is happening for a mailbox that has already been migrated to O365 (we have a hybrid environment), so please do not answer with your stock answer that you've answered every other post with: "This happens for mailboxes that have not been migrated to O365. Your mailbox is likely still on a dedicated exchange server. You'll need to request your Outlook administrator migrate your mailbox."
That is NOT the case with me, or many others that have had this problem as I see from researching this problem.