Does the data match what you see on the admin portal - https://admin.microsoft.com/Adminportal/Home?#/reportsUsage/OfficeActivations?
If the users have who activated Office for desktop clients/apps across platforms and are missing last activated date, you should create support request.
In my digging, I have users who have activations but 0 on all client types. All of these don't have last activation date