First of all I would like to say that I currently have a working pbx, as I’m able to receive calls and make outbound calls.
it happened few times when I try and make an outbound call using a Cisco phone I see message saying “SessionOpen” and then “Connected” but I don’t hear a ring tone or the other party. on the other hand, the other party is able to hear me.
when I hang up the call and try again, it seems to work fine.
it happened number of times. and I’m not sure if this is an asterisk issue or provider issue???
it could be a firewall, I think you are right, I have the phone setup behind a pfsense firewall, maybe at the first try it open up the port, and on the second try the call goes through.
VOIP.ms is inexpensive for a reason. Try a different VOIP.ms server. Try a different provider, i.e. Callcentric or Flowroute. I’ve had similar events, but not in over a year.