Hi! I have 3cx almost up and running. If I can get one last thing working then I'll make the purchase. Here's my config: 3cx FREE on AWS Firewall checker says we are A-ok 2 phones at home office, both Grandstream GXP 2000 Inbound calls work perfectly from the outside (I use callcentric to provide the trunk). I can hear the caller and they can hear me. I can hear sidetone on the handset, etc. All seems ok. Problem: Calls between extensions ring, but when answered there is no audio either direction. There is also no side-town in the handset. Any ideas?? Thank you.