Disconnect from the internet
Temporarily disable Wi-Fi or unplug the Ethernet cable.
Manually enter your product key
Go to:
Settings > System > Activation > Change product key
Enter the key you received and continue.
Reconnect to the internet
After the key is accepted, turn your connection back on and restart the PC.
🛠 Other helpful checks
Activated on another PC?
If your key is transferable, you may need to remove it from the previous device before using it on a new one. Make sure it’s only in use on one device at a time.
Reactivating after a hardware change?
You can try reactivation through your Microsoft account:
Settings > Activation > Troubleshoot > I changed hardware on this device recently