I had an issue like this following a recent update. Two email accounts, neither would update. Cant get into settings, it's as though they dont exist. Cant remove them, they're not there. Cant add them they already exist. Cant uninstall Outlook. Had to do a complete reset.
Make sure you have a good back up. Make sure your MS account is the first one you add otherwise you dont getyt opportunity to restore. Also, dont make the mistake I did of having double authentication turned on. If you do yo uneed to get the code from a text they send you but you're unable to read it. Turn double auth off untoil you've done the restore and then switch it back on again - if you use it that is.
Good luck!
(now mine is OK i seem to have caught the issue where wifi keeps dropping!)