@Steffen Sledz
Thank you for the post!
Since this has to do with an Office license for Home & Business, I've added the "office-online-server-general" tag to see if someone from their team can look into this issue. Additionally, I did find some documentation that might help with your issue:
Resource: Transferring Office 2016 Home & Business
I'd also recommend reaching out to the Microsoft 365 and Office forum.
If you have any other questions, please let me know.
Thank you for your time and patience throughout this issue.
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