WinLink: gateway connection issue

I have a question for any WinLink experts here. Someone in my club set up a new WinLink gateway for VARA FM and 1200 baud packet. He can connect to his own gateway (using a second rig, computer, and SignaLink), but I can't and several others have tried and can't connect to his gateway either. Whether attempting via packet or VARA FM, and whether trying to connect, send a ping, or calibrate with his gateway, I get the same "no signal" error. I've tried two different antennas (Comet GP-3 vertical and a 5-element yagi), I've tried power as low as 5W and as high as 50W, I've tried various SignaLink settings, all with no luck. Yet I can connect via multiple other packet and VARA FM gateways just fine. The troublesome gateway is 16 miles ENE of my location and SCADACORE says we have a clear line of sight. The gateways I can connect to no problem are 0.25 miles, 16 miles, and 25 miles away in other directions. Several of us have been testing and researching, trying various things for weeks now with no progress. I am using the paid, licensed version of VARA. Any suggestions? Thanks in advance!