Replaced after market radio three times still not working

I bought the truck with a after market radio in it. One day while driving the radio cut out, so I replaced it (twice) and still couldn’t get it to turn on. I have 12 volts switched, 12 volts constant and ground. I find it hard to believe that three radios are all bad. Any suggestions? Assistance will be greatly appreciated. Actually the truck is a Scottsdale, but that wasn’t listed, or C-10.