Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi, Signing in at Services & Subscriptions of the Microsoft Account associated with your 25 Offices. Here is a direct link: https://account.microsoft.com/services Not only should signing in activate any unactivated you should see all 25 instances of your Offices from where you can reinstall them (if you can figure out which one belongs to which computer)
Also, open one of the Apps on an unactivated Office, e.g. Word>File>Account>Top left hand side of the page it should show you the Microsoft Account associated with the Office and should be signed in. Also, on the same page it may show the Office is Activated or not Activated.
Note: You can change licences. See this article: Manage multiple one-time-purchase Office installs that use the same Microsoft account - Microsoft Support
Note, 25 licence is the limit for one Microsoft Account. Personally I would not recommend more than 20.