Work through activation methodically.
Most activation problems become easier to diagnose when the product, platform, account, and error are checked together.
The key is shown as invalid
Check for typing errors if manual entry is allowed, confirm that the key matches the exact product and version, and use the official activation route in your delivery email.
The key has already been used
Do not buy another key or share the key publicly. Sign in with the account originally used for redemption, then contact support with your order number and a redacted screenshot.
The product will not activate on this device
Confirm the operating system and edition match. A Windows-only product cannot be activated as a Mac product. Also review any device or transfer limit in the listing.
Office still shows an old license
Check which account is signed in under the app’s Account page. Removing old credentials or licenses can affect access, so follow official Microsoft guidance or ask support before making changes.
Activation asks for a different account
Use the account that was linked during redemption. If you redeemed with another email, sign out and back in only after confirming which account holds the license.