Switch Outlook App from institutional to private license

Question

Dear MS 365 community,

I have the following issue:

I was using my Outlook with a university MS account / my university email adress during my studies at that university. Now I graduated and my university email account is deactivated, I tired to switch Outlook to my Office Family license that I had purchased and that is active - without success. All other Office Apps (Word, Excel, etc.) can be started (ignoring the error message while trying to log in with the university account), but Outlook does not, at all. It does not recognize the email adress linked to my Office Family license.

The MS Windows support team already de- and reinstalled Office, and deleted the university registration account from my system, but could not resolve the issue (chat time with the Windows Support team on this issue was 2,5h).

I cleansed the registry from all entried referring to my university account. After restarting the computer, this specific entry reappears:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Profiles\Outlook\9375CFF0413111d3B88A00104B2A6676\00000005

Previous key I deleted was ending with 00000004

Help is greatly appreciated! Thanks.