we have a call flow of sending calls to a ring group, if no one answers it's forwarded to an external answering service. it calls the number but no audio in either direction. If we use find me follow me to an external number it does the same thing. I saw on another form to test audio by adding an announcement in-between.....strange thing is this fixes everything even with a blank announcement. This works for the inbound route (kinda, I would like this not to be the fix) but it does nothing if we actually transfer a call to a cell phone. we just get dead air but Astrisk thinks the call is fine.
I don't know how to troubleshoot this as the logs look fine, the call is connected and packets seem to be flowing but neither side hears anything. I have all RTP ports forwarded 10,000 -20,000 and no issues with any calls other than external forwards. the system knows its public IP.