This is a known issue on Microsoft's side affecting a small percentage of users using the SSO functionality. Thankfully, there is an easy workaround.
If you click on the three dots next to your emails addresses, and then you choose "Sign out and forget" on both accounts, you should be able to log in as usual the next time you try to log in. You then need to type your email and password again. You only need to do this once to resolve the issue.