Hi @Elke Kaercher ,
Welcome to Microsoft Q&A!
To be honest, this is not the scope of "Microsoft Exchange Online Management" support.
Is the "license number" you mentioned a product key? If so, I made some queries for you, hope it can help you.
If not, please understand that the tag “Microsoft Exchange Online Management” is for general questions about Exchange Online. Or you can repost your question in the Results in Microsoft 365 and Office - Microsoft Community
Regards
Shaofan
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