US calls not coming through

[#1]

Using VOIP with Plusnet Hub 2, a Grandstream adapter and the Andrews & Arnold service, I notice that phone calls from the USA are being cut off after one ring. What can I do to prevent this?

[#2]

@MisterW   @outcast 

Waiting to hear from A&A Support but would be grateful for your thoughts.

[#3]

@redsox9 I cant quite see why calls from the US would be treated any differently by either A & A or your Grandstream. 

My guess (and its just a guess!) is a poor internet connection to the US endpoint.

A SIP log from the Grandstream (if it can provide one?) or a Wireshark trace may provide some insight.