Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
I have the same problem. I have to use Outlook for my work e-mail due to institution policy that does not support the calendar syncing without Outlook for Outlook365. Gmail sync with the same app worked fine. This problems showed up a few weeks ago and I cannot get rid of it. I have re-installed the app which fixed it for a few days but the problem recurred with no changes in the settings on my part. Message notifications arrive but the inbox does not update. Resetting the account did not solve it.
I have found a frustrating work around which may be a clue. If I force stop the application from the app manager (remove its background processes from memory) THEN reboot the phone it syncs fine for perhaps a few hours. If I do either of these without the other, no luck.
It's really shameful how Microsoft is not devoting the resources to solving this problem. The tread makes it clear, it's at least a 2+ year old problem.