Hi Lars,
I am Sumit, an Independent Advisor.
No OEM keys do not expire for the lifetime of the device.
Get help with Windows 10 Activation errors:
https://support.microsoft.com/en-in/help/10738/...
https://support.microsoft.com/en-in/help/12440/...
To better diagnose the issue,
- Right-click Start button and Choose Windows Powershell(admin) and type in the following command:
slmgr.vbs /dlv
You will get a window, take a screenshot and send the same in the next reply.
- Run the activation troubleshooter and send us the output.
Using the Activation troubleshooter-Windows 10
https://support.microsoft.com/en-in/help/20527/...
How to include a screenshot in your post
https://answers.microsoft.com/en-us/windows/wik...
Please let us know if you need any assistance in posting.