1993 2500 Chevy Aftermarket Radio Harness issue

Hello, I have got 1992 Chevy Silverado 2500. I am currently having wiring issues on the radio. To answer so quick questions the factory harness was not been cut off it has been plugged in to an adapter to splice to the radio. The fuse on the back of the radio is good, using a test light I have checked my fuse block under the radio fuse and I am getting power but when I trace it back to the factory harness I have no power this is on the 12 V ignition wire(Red). I do have power on the yellow 12 V constant memory wire. So just taking a shot in the dark I don't think it's the ground on the factory harness otherwise I would not have any power on my 12 V constant (Yellow). Does anyone have any suggestions or has had the same problems as me?