Win 8.1 Activation

Hi, the motherboard replacement is probably the key detail here.

If the Windows 8.1 license was OEM, it may have been tied to the original motherboard. In that case, Windows can work for years on the old installation, but after a reinstall it may no longer activate on the changed hardware. If it was a retail license, you should have a better chance of reactivating it, possibly through phone activation if that option is still available in your region.

Try entering the original product key again and running `slui 4` to see whether phone activation is offered. Do not post the key online. Also keep in mind that Windows 8.1 is out of support, so activation support options may be limited. If the key is OEM and the motherboard was changed, Microsoft may treat it as a different PC.