We have migrated all of our users to Office 365. One user, who has been able to access her email just fine for the last couple of weeks, is all of a sudden unable to. She logs into the Office 365 portal and can access any of the other office tiles, but when she goes to use the Mail one, it gives her a message that says she has been logged off. We've had her try it from a couple of different machines and she gets the same thing. I have checked and she is properly licensed. I do not see anything wrong in her Office 365 user config or her AD config.