[SR-Users] Trouble with Kamailio/RTPEngine and NAT/Firewall

Hi, I have a Kamailio/RTPEngine setup with Asterisk on a couple of EC2 instances. There is a public IP and it's setup to accept any ports from our IP addresses. If I DMZ my machine behind my router, I get audio, otherwise I don't get any audio, but the SIP portion of the call connects properly. It isn't specific to my network either, it's the same for my partner on his network. I'm assuming that NAT is getting in the way, although I'm not 100% if it's that or if it's a problem opening ports. I have tried with SIP/RTP Passthrough enabled without success. Can anyone provide some guidance here? Thanks, PJ Slauta