So I've got a remote worker and I set him up with the Asus AC1900 router and I have the RT-AC68U I have SIP ALG disabled on both routers. On the phones, I usually switch STUN to Disabled under NAT because I had issues with clients Running latest version of 3CX. To test I'll call my cell phone, hit the conference button and then dial the extension of my remote worker. It rings he picks up but we cannot hear each other. Same when he tries it. I tried every combination, SIP ALG on & OFF along with NAT STUN/ Disabled. Nothing works. Not sure where to look next.