Windows shows this code when Microsoft's activation server has rejected the key. The usual message reads "The activation server determined that the specified product key is blocked."
Why it happens
There are three real causes. It helps to tell them apart, because each one has a different fix:
- The key is already active on another computer. A license for one PC can be active on only one computer at a time.
- The key is for a different edition. A Windows 11 Home key will not activate Windows 11 Pro. A Pro key on a Home PC works differently: Windows switches the edition to Pro first, with no reinstall and no lost files, and our installation guide has a chapter with the steps.
- The key has been blocked by the activation service. No setting on your PC can undo that.
A temporary problem with the activation server can produce the same message, so rule that out first.
How to fix it
1. Wait and try again
Before anything else, rule out a temporary problem. Wait a few minutes and repeat the activation from Settings > System > Activation.
2. Check that the key matches your edition
Open Settings > System > About to see which edition is installed, and compare it with your order.
3. Release the key on the previous computer
If the key was active on another computer, remove it there first. On the old computer, open Command Prompt as administrator and run slmgr /upk, then slmgr /cpky. Then enter the key again on the new computer.
If none of this works
Then the key may be blocked, and nothing on your PC will change that. Write to us with this error code and your order number. A key that does not activate is covered by our Lifetime activation guarantee, and support is available 24/7 from our contact page.
