cd player/radio is not turning on on 2004 Chevrolet Trailblazer

ok i bought an aftermarket cd player for my trailblazer. i took the stock one out and hooked up the aftermarket one and it didnt work. so then i tried to hook the factory cd player up and now it wont even come on

best to have a stereo shop install these as there are tricks that they know from doing it everyday