Was having the same issue. When I was following the instructions of a previous poster, I noticed that the MD URLs were missing. I clicked the link to 'Restore default MDM Urls' and 'Restore default WIP URLs', remembered I was there to set WIP to 'None' then clicked save. Went to the newly built system I was trying to register and it worked.
Currently running onsite AD hybrid. So our machines are joined to a local AD server first.