Most activation problems are not about the key at all. They are about which Microsoft account is signed in, which edition the installer picked, or whether the PC could reach Microsoft at that moment. Work through the first section before you touch the key.
Try this first — fixes 70 % of cases
- Check the accountOpen any Office app → File → Account (Windows) or Word menu → About Word (Mac). Is the signed-in Microsoft account the one you used at setup.office.com? If not, sign out and sign in with the right one.
- Check the editionWindows: Settings → System → About shows the edition. A Pro key activates Pro, not Home — change the key from Settings → System → Activation to switch edition.
- Check the clock and connectionA wrong date/time or a captive Wi-Fi portal blocks activation silently. Set the clock to automatic and open a web page to confirm you are online.
- Run Microsoft's troubleshooterWindows: Settings → System → Activation → Troubleshoot. Office: Microsoft Support and Recovery Assistant (linked from our guides).
- Restart and try once moreActivation servers are occasionally busy; a retry ten minutes later clears transient errors.
Error codes and messages
0xC004C003 · Windows
What it means: The activation server reports the key is blocked or has been used on a different PC.
Fix: If you bought the key from us, contact us with your order reference — we verify it against our batch records and replace it under the guarantee. If the key came pre-installed on a PC it is tied to that hardware and cannot move.
0xC004F050 · Windows
What it means: The key is valid but not for this edition (for example a Pro key entered on Windows Home media that cannot upgrade).
Fix: Settings → System → Activation → Change product key and enter it there instead of during setup; Windows switches edition automatically. If that fails, reinstall choosing the matching edition.
0x803FA067 · Windows
What it means: Windows cannot reach Microsoft's activation service or the PC has no digital licence yet.
Fix: Check the internet connection, run the Activation troubleshooter (Settings → System → Activation → Troubleshoot), then enter the key again.
0xC004C008 · Windows
What it means: The key has reached its activation limit.
Fix: Retail keys can be reactivated after a hardware change through the troubleshooter ("I changed hardware on this device recently"). If that is refused, contact us.
0x80070005 · Windows
What it means: Access denied — usually a permissions or antivirus block during activation.
Fix: Run Command Prompt as administrator and enter slmgr /ato. Temporarily pause third-party antivirus if it still fails.
"Unlicensed Product" · Office
What it means: Office installed but cannot find a licence for the signed-in account.
Fix: File → Account → Sign out, then sign in with the Microsoft account you used at setup.office.com. If you never redeemed the key, do that first.
"This key has already been redeemed" · Office
What it means: The key was linked to a Microsoft account already — often yours, from an earlier attempt.
Fix: Sign in to account.microsoft.com/services. If the product appears, install from there — no key needed. If it does not, contact us.
0x80070190 / 0x8004FC12 · Office
What it means: Activation service could not be contacted or a system component is out of date.
Fix: Install pending Windows updates, restart, open Office again. Run the Support and Recovery Assistant if it persists.
"Product deactivated" · Office
What it means: Microsoft revoked the licence — typically because a payment was reversed by the original purchaser (grey-market keys).
Fix: Keys bought from us are never in this category. If this appears on a key from elsewhere, you need a new licence.
"We couldn't verify this is a genuine copy of Office" · Office for Mac
What it means: The Mac licence file is stale or belongs to a different account.
Fix: Quit all Office apps, run Microsoft's Licence Removal Tool, reopen Word and sign in again.
Phone activation (when the internet route refuses)
Microsoft still runs an automated telephone activation service, and it resolves the "already used" family of errors when the hardware has changed or an earlier attempt half-completed.
- Windows: press Win + R, type
slui 4, choose your country. Read the installation ID to the automated line and type the confirmation ID back. - Office: File → Account → Change Product Key → enter the key → choose I want to activate the software by telephone.
If you would rather not do this alone, call us during business hours and we will stay on the phone while you go through Microsoft's automated steps.
Reinstalling later
Because every licence we sell is retail, you can reinstall on the same device as often as you like, and move Office to a replacement device when you retire the old one. Keep three things: your order e-mail, the Microsoft account you redeemed with, and the order page link (it never expires). Our article on moving Office to a new computer has the exact order of steps.
Our guarantee
If a key we supplied will not activate and the steps above and a call with us do not fix it, you choose: a replacement key from a different batch, or a full refund to the original card. The window is 30 days from purchase and the full terms are in our refund policy. You will not be asked to "prove" anything beyond the error you are seeing.