I did have that on a few days on my own.... but it resolved itself after a few days..
(maybe its something with the moving servers of people accounts around?)
Mind you, i dont keep a 'hard' client anymore generally for my email (outlook, etc), I do remember in the past, that when it was open and say connected to the email.. i would have issues downloading on the iOS app. Close the client on the PC, would then download fine. (like it was only allowing one authorized connection at a time)