Office 365 was installed 12/2015.

This morning a yellow banner appeared across the top of Outlook stating that Outlook was deactivated--click to activate.

I had to fish around for the product key, enter same locally + credentials, then do again on a website and OL was activated.

I called MS support for a reason why. No local log to explain why. No (good/specific) reason and no proactive action to avoid this mess going forward.

Given the preceding, there's no reason not to expect this to randomly again occur and disrupt work.

Has anyone else run into this problem?

Mark