[ICOM] Need help with IC-746pro and Amp

[n5ohl]

I have a new Icom IC-746pro. When I try to use my Ameritron 811H amp the rig will trip the relay on the amp but the SWR shows very high on the 746pro. When I have the amp in standby or off the SWR is almost 1:1 and the radio puts out power. I radio set on about 30 watts output. I am not using the tuner in the radio, it is off. I am using a resonant antenna with very low SWR. I had this exact same setup on my previous radio, a Kenwood TS-850. It ran the amp just fine. I purchased an after-market amp keying cable that is made for the 746pro. I have also tried this with a straight cable and I get the same results..

Any help would be great,

Jim N5OHL