I have a GXP2130 phone configured on a voip.ms subaccount for outbound calls. I also have a DID registered at voip.ms, which I have pointed to the correct sub-account for the GXP2130. I can make outbound calls without any problem, but I cannot receive inbound calls. The server at voip.ms for the DID, and the server the phone is registered on, are the same. If I direct the DID to a Yealink phone, the phone rings immediately, but if I redirect the DID back to the GXP2130, it won’t ring. Nothing happens, no busy signal, nothing. It won’t even drop the call, just dead silence. If I redirect the DID to another grandstream GXP16xx series at a completely different location, the same behaviour, the call does not go through.
What am I missing on the configuration of these Grandstream phones? voip.ms tells me the problem is with the configuration of the phone, and is not on their end.