I kept on getting the above error message when executing New-OfficeWebAppsFarm even though my Office Web Apps (OWA) server is joined to a domain.
My setup is like this: Server A has SP2013 installed on the physical machine, and hosts a virtual domain controller. Server B has OWA 2013 installed on the physical machine. Server A and Server B is connected using a crossover network cable.
The problem turned out to be the network settings on my Server B where OWA is installed. In the IPv4 settings, I specified a static IP for the server but did not specify a preferred DNS server IP. I set the DNS server IP to be the IP of the domain controller (virtual on Server A) and was then able to create a new farm!
This KB article helped me to solve this issue.