HELP: DC's failing to register with DNS server in test lab

Hi all,

I'm currently building a test domain in a VMware lab, that replicates my live domain. I started by adding a Virtual DC to both domains in my forest (empty root domain and user domain). Once replicated I chopped their connections and moved them to a private network.

However I'm stuck on first base, as I can't get either DC to dynamically register itself with the windows DNS server (clean install) I have stood up on the same private network. All VMs can ping each other, but running ipconfig /registerdns on either DC records the error shown below in the event log.

The system failed to register host (A or AAAA) resource records (RRs)for network adapterwith settings:AdapterName:{60E1F11F-2529-4686-AEDE-27FFAF39B2F6}HostName: ROOTDCNAMEPrimaryDomainSuffix: rootdomain.company.com
           DNS server list :192.168.0.1Sent update to server :<?>
           IP Address(es):192.168.0.67The reason the system could notregister these RRs was because the DNS server failed the update request.The most likely cause of thisis that the authoritative DNS server required to process this update request has a lockin place on the zone, probably because a zone transfer isin progress.You can manually retry DNS registration of the network adapter and its settings by typing 'ipconfig /registerdns' at the command prompt.If problems still persist, contact your DNS server or network systems administrator.

- All VMs are running Server 2012R2 with static IPs

- All VMs are on 192.168.0.x addresses and can ping each other. Firewalls are all disabled for testing

- All machines have "Register this connections address in DNS" enabled

- I have 1 forest and 2 domains (rootdomain.company.com and userdomain.company.com)

- On the DNS server, I created a forward lookup zone called company.com. I also created a reverse lookup zone with address prefix 192.168.0.x. I enabled both secure and non secure updates on both zones, and disabled zone transfers on both zones. 

- All VMs point to the DNS server as gateway and DNS server.

I'm stuck as to why the DCs are not registering on the DNS server. I could try adding the records manually, but I shouldnt need to do that.

I would be VERY grateful for any help or advice on what step I am obviously missing ? 

TIA