Dear @Sebastian Morawski,
Thank you for posting your question in the Microsoft Q&A forum.
I apologize for any inconvenience you may encounter when using our services/ products. Based on your description, kindly try these following steps: Please sign in to Microsoft account | Sign In or Create Your Account Today – Microsoft.
If you can sign in via the above link, then kindly use this link to check which account contains the correct BitLocker recovery key: Microsoft account | BitLocker recovery keys.
If not, please refer to this article to recover your account. Help with the Microsoft account recovery form - Microsoft Support
I sincerely hope you understand that the initial steps I suggested may not have completely fixed the issue, as there may still be underlying causes that have not yet been identified. I am here to work closely with you, troubleshoot effectively, and explore every possible solution to ensure the best possible outcome.
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