Microsoft Account Conflicts

 Last weekend, I took an exam online for my distance learning.
As usual, I logged in to the student's room on my university website and downloaded the test paper and the answer sheet.
The answer sheet was a Microsoft word document, so I started writing my statement and clicked the save button AS USUAL.

The next day, I got a phone call from university staff, who noticed my test answer was invalid.
I studied what caused this failure and assumed that my personal Microsoft account and student Microsoft account haven't been compatible since this month.

This is a message when I log onto the student page to join an online class.
I used my personal Microsoft account and was rejected from the online classroom.

I will need to use my university Microsoft account to work on my papers from this year instead of my personal ones.

Do I need drastic changes to my Microsoft account settings?