Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
I found this method to enter the new Military product key I purchased as the only way to upgrade. It seems Microsoft doesn't want to upgrade the Military version automatically.
Go here and sign in:
https://portal.office.com/Commerce/ProductKeyStart.aspx
I entered my new Military Office 365 product key on this page and it updated my Office 365 for another year.