amp help ground install

I have an old school Rockford Fosgate Punch amp, 8 inch sub and a Pioneer DEH-24UB head unit. I had the amp and sub hooked up in my old car and everything worked fine. I have recently tried to install it in my new car with the new cd player and I can't get the LED light to come on, therefore...

i just connected my 4 channel amp (2 channels to 6 speakers (my 6x8 my tweeter and my 3.5) (2 channels to my rear 6x8) i think i have a bad ground cause i see the amp light dim a lil with my highs on only after about a full song it sounds like the amp isnt putting its full potential can i...