Ever seen a Refresh your alerts message in Office 365?
You could follow the instructions:
Please sign out and sign in again
This is exactly what you need to do! But what is causing this warning?
I’m getting these warnings every time my laptop falls asleep. Then when I get back to my laptop an hour later, I’m getting these warnings. So Office 365 seems to protect it’s alerts. I guess you shouldn’t leave your browser sessions open while you’re leaving your desk for lunch.