My wife works for a large company that has their own internal phone system with direct inward dialling. So I can dial my wife directly from outside.

This works correctly with my landline, my cell phone and via the Viopo softphone credentials, but when I use my Viopo phones connected via the GrandStream HT502 I connect properly only about 10% of the time.

If the phone rings (sometimes it does not), from her perspective it disconnects the call immediately she picks up. From my perspective, I hear no ring tone and (maybe) a click indicating connection and then nothing.

All other calls we have made so far seem to work OK, but if we cannot get this fixed it is a show-stopper.

My hardware setup is:-

bridged cable modem with static IP <--> linksys router running DD-WRT<--> HT502 with static ip address in bridged mode