amp not working

I got this used legcacy 600w 4 channel amp. I pretty sure I got everthing hook up, the amp lights up but no sound from speakers or sub? It's got a protection circuit on it and the led doesn't light up? Any specail way I have to hook it up? Got the power wire, ground, power antena and rca's hook up along with the wires to the speakers. I got two 4 prong plug's and not to sure about and it says above it high's?

good place to start would be to tell us a little more about what you have...what kind of deck...are the two four pin plugs at the back of the deck...do they have the colors white, grey, green, purple, and each of those with a stripe...what kind of car...is there a factory amp somewhere...and finally...how many rca jacks on the back of the deck?