Hi Tvnap,
Thanks for posting in the community. We are happy to help you.
According to your description, you purchased Microsoft 365 Family Military Appreciation Edition, but when you tried to enter the product key to activate Office, the error message popped on.
Please try the following steps to redeem the product key with your Microsoft account, then check again.
- Go to https://microsoft365.com/setup
- Sign into your Microsoft account (Hotmail, Live, or Outlook.com). If you don't have a Microsoft account, please create a free Microsoft account using an existing email address.
- Enter your product key, without hyphens. Follow the prompts to finish the redemption process.
After that, please run one Office application, sign into your Microsoft account to activate Office.
If any error message appears when you sign into the account in the Office application, please post back and let us know. We will keep on assisting you.
We look forward to your response. Thanks for your cooperation.
Sincerely,
George | Microsoft Community Moderator