The Neverfail DNS tools provided for WAN deployments
Will only function if the server is a domain member. This is because the tool queries Active Directory for the list of DNS servers that require updating.
This is expected behavior and cannot be changed.
DNSScripter.exe shipped with all versions of Neverfail Heartbeat upto and including V4.3.5.
DNSupdate.exe shipped with all V4.4 and later versions of Neverfail Heartbeat.
Please see the document titled Td-H - Environmental Prerequisites for Neverfail Active Directory and DNS requirements.