email is used with more than one account

Hello community,

I have a problem with my Teams App.

Background: I was enganged in a university and used my own PC for home office. I had an accout from university which I used to sign in in Teams. But however this happened, my uni account connected to my private mail account. When I open teams now, sometimes it says "It looks like this email is used with more than one account from Microsoft. Which one do you want to use?" and I have the choice between "Work or school account" and "personal account". If I choose "personal account", enter my log in data and press enter, it nevertheless tries to connect via the uni account - which doesn't exist no more - and tells me to contact my administrator for activating the account.

In the "choice window" it says "Tired of seeing this? Rename your personal Microsoft account" underneath, connected with a link. But pressing the link nothing happens.

I also contacted my university because of this problem but also a proper reset didn't work at all. I have the same problem on my phone...

Tonight I contacted the Microsoft support, who couldn't help me neither. He recommended to ask the techcommunity of Microsoft... So here I am. 

Today in the morning I also had a chat with a Teams Support from Microsoft. I was able to connect via Web App to my private Teams Account. But the issue is, that I want to communicate with people from the uni via Teams and when they send me an invitation, Teams automatically tries to connect via my no more existing uni account. I would just love to delete this university account...

Puh, that's difficult. I'm no native speaker, so I hope, that you understand my issues and I hope that there is anyone who could help me.

Thanks in advance!
Nicole