Had my perfectly legal W10 activated for couple of years now (build 17763.316 currently) but after changing the motherboard, CPU and memory, and after rebooting everything I didn't even notice it's not activated anymore until the transparent "Activate now" label showed in the lower right corner. Tried re-applying my original key - nothing, error 0xc004c060. After Googling a few solutions, I tried troubleshooting "recently changed hardware" - nothing. Tried calling them with my installation ID - it's not recognized. Tried rearming, switching back to the "default" key and re-applying mine - nothing. Even managed my M$ account and removed the old PC device... Any help appreciated, wouldn't want to format my ssd if there's a chance I could fix it.
The key used might have been blocked by the MS. Use windows activation troubleshot for hardware change. What version/edition of Windows do you have now?
The one Hardware change in Win 10 that is not allowed is the Motherboard. If you change Motherboard, Microsoft considers that a New PC & you need a new License.
OP still did not say whether using Win10 pro or Win10 home run winver to determine win10 version and edition