I have a problem logging in to Forms from the Office.com starting page OR directly. I get or a redirection loop (attached error message). Tried with several browsers, i can login only using Internet Explorer (doesn't work with Chrome, Edge, Firefox). My OS is Win10, i am using Office365 for education.
I am the administrator for the tenant, nobody else is having this problem. :)
I tried deleting cache/cookies, disabling/reenabling Forms license for my accout, enabling/disabling "Do not track requests", browser unistall/reinstall, nothing helped.