I have multiple VoIP Providers that supply lines to multiple businesses all managed by one 3CX system. All of the VoIP Providers lines work fine except for one (NexVortex) where I get one-way audio on Outbound calls only. I am using an Apple Airport on Windows 7 network, have run Firewall Checker and recieve a failure on Phase 2a with exit code 2. I have been searching these forums for DAYS trying to figure out why this is happening on this VoIP provider only and not the others. Any help would be appreciated. Joe.