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I am sorry to hear about the hardware failure. Having to rebuild the PC and then finding that Windows 11 Pro is no longer activated can certainly be frustrating.
Since the motherboard was replaced, Windows may no longer recognize the rebuilt PC as the same device associated with the previous digital license. Microsoft identifies motherboard replacement as a significant hardware change that may require Windows to be reactivated.
If your Windows 11 Pro digital license was linked to your Microsoft account before the hardware failure, please use the Activation troubleshooter to reactivate it:
- Make sure the rebuilt PC is connected to the Internet and that Windows 11 Pro is installed.
- Sign in as an administrator using the same Microsoft account that was linked to the digital license.
- Go to
Settings > System > Activation > Troubleshoot. - Select
I changed hardware on this device recently, and then select Next. - Sign in with your connected Microsoft account when prompted.
- From the list of devices linked to your Microsoft account, select
This is the device I’m using right now, and then selectActivate.
Please also make sure the Windows edition on the rebuilt PC is Windows 11 Pro, the edition must remain the same before and after the hardware change for the digital license to reactivate.
If your previous device does not appear in the troubleshooter, verify that you are signed in with the same Microsoft account that was associated with the Windows 11 Pro digital license.
For reference:
Reactivating Windows after a hardware change | Microsoft Support
I hope this helps you get Windows 11 Pro activated again after the rebuild.
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