Moving Phone to new Mobile Device Manager

Back in June I attempted to Migrate Desktop Central to SQL database, which failed and left Desktop Central unusable. I attempted repair per instructions provided from Manage Engine Support but nothing worked so I reinstalled Desktop Central on the Server. As a result the few phones I had on the old instance still have certificates for enrollment to Mobile Device Management, I cleared most of them out but it has been awhile since I did it and I have found a phone that will not join the new MDM because it still has management certificate from old instance, how to I remove this from the phone so I can join it to the new Mobile Device Management?