0xC004C008 means the activation server determined the product key can't be used right now — most often because the key has reached the number of machines it's allowed to activate. KMS and volume keys have activation limits, and once that count is hit, further activations are refused with this code until the count frees up.
Common causes
A single key reused across more devices than it permits.
A KMS client key pointed at a host that has too few active clients to activate.
A shared online key that's already maxed out.
How to resolve it
The dependable fix is to activate locally rather than fight over a shared key's count. KMSPico runs its own KMS host on your PC, so your activation never competes for a remote key's limit — it simply applies the matching GVLK and activates. If you're doing it manually, clear the current key with slmgr /upk and re-run the slmgr sequence against a working host.