Hi Valentin Glas,
Welcome to Microsoft Q&A,
The error indicates that your subscription has been blocked due to inactivity for more than 200 days.
If your subscription/tenant has been blocked due to inactivity for a long time, there’s only a short window of ~ 20 days where Microsoft Support can still restore it. After that, it may be permanently deleted.
Suppose you don’t have any important resources, or you have passed the 20 days after the inactivity in the old subscription/tenant. In that case, the easiest option is usually to create a new Azure subscription (or new tenant if needed) and continue using Azure there.
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