New
#1
The first thing that comes to mind is either a slow connection or overworked server.
The time on either your computer or router could cause it if it's set wrong. I'm not sure how far off it has to be though I do know that being off by seconds won't cause it.
Edit:
Just checked my Sign in to your Microsoft account---https://outlook.live.com/owa/ email and it worked in both IE and Chrome, Not much help I know but it works in Canada.
There is a fix for this problem coming out shortly.
Office 365 Service Status