Potentially you have multiple email addresses tied to your MS account. Do you know what email account your xbox was opened under? It might be the same as your Teams account. This happened to me with my Skype account which somehow had an old email address I used for a non-profit at one time. When I did some digging, I found that that email was tied to my Skype account which was all tied to my Microsoft Account so when I tried to log into new services with what I thought was my hotmail that was used for everything, it was looking for this other-never-really-used email. When I deleted that bad email and added the hotmail to my skype account and made my microsoft account have only my hotmail tied to everything, I was able to sign-up for new services with my MSA and it all worked again. Maybe? Let me know if that isn't it and I can do some digging over here.