I've had this happen before, and honestly I'm not 100% sure what fixed it. It's working fine for me currently, however.
If it keeps happening, try deleting your web browser's cache/temporary files (make sure you don't delete your saved passwords, Autofill form data, etc. Resetting your cookies may be a good idea, but note it'll automatically sign you out of all websites you're currently signed into).
Also try using another web browser, if you have one. Google Chrome is what I'm currently using, but honestly any modern browser shouldn't have any issues...
You may have to allow pop-up windows for the website, also, seeing as how the Microsoft option opens a new window entirely.