Can't register for private microsoft account

A few years ago, I registered my domain becker-mainflingen.de with Microsoft and had my emails there. This account has been canceled for some time now.

In order to use various Microsoft services now, I need to create a private Microsoft account. When I register with an email address from the above domain, I get an error message saying that I am not allowed to use a business account.

How can I activate my domain here?