Hello @André Boonstra ,
Thank you for reaching out Microsoft Q&A.
You are getting the error because the tenant has been blocked due to inactivity.
The only way to get this reactivated is through the Global Support Team by contacting them via the global support phone numbers
for additional information follow the document: https://learn.microsoft.com/en-us/entra/fundamentals/inaccessible-tenant
Hope this helps. Do let us know if you any further queries.
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Regards,
Goutam Pratti.