outlook keeps sending me back to the sign in page

almost always cookies on the microsoft login. does it work in a private or incognito window? if yes, clear cookies just for live.com, microsoft.com and office.com rather than everything, then sign in fresh. if incognito loops as well, check the computer clock is set to automatic, a drifted clock makes the login token expire the moment it's issued. and oddly, ticking stay signed in on the login page has fixed this for me more than once.