If you encountering registration and verification errors with a 365 installation, enter the following commands in a command prompt to list and deactivate office licenses attached to the computer. We typically delete all of them and then re-register. Change the version number as appropriate for your environment.
Get licenses list:
C:\Program Files\Microsoft Office\Office16\cscript ospp.vbs /dstatus
C:\Program Files\Microsoft Office\Office16\cscript ospp.vbs /unpkey:XXXXX (last 5 of key in previous list)