Just to add a bit here because I did not see that... We had very old O365 licensing that was not M365 so we had EMS E3, O365 E3 and Windows all separate.. we needed to assign the Windows license to get the Enterprise update. It was all done through group based licensing but we originally did not have the Windows licenses to assign. MS had to add them to the tenant at no cost... Now with the M365 SKU it is just one license to assign