How to fix microsoft Authenticator loophole when old phone is gone and no backup was made

I had Authenticator on my old Iphone for logging into my school outlook account. Then i got a new phone. I wipped my old phone and sent it away for refurbishing. Now I tried to log into my school account on my new phone and the Authenticator app seems to send me in a loophole. Every time I try to reactivate my school account it wants a code (6 digit) or a number (2 digit). But I do not receive notifications of both these codes on my new phone. I think it want's me to verify it from the old phone (that I do not have anymore). I read online that you have to backup your account. I did not do this.... How do I get out of this loop?!