problems with new pioneer

i just got my new headunit (pioneer deh-p6600) and i connected all the wires but the HU wouldnt turn on, i tested to see if the HU was defected by putting the red and yellow wires on my postive battery terminal and my black on the negative, everything went fine and the headunit turned on, but when i connect all the wires in my car it doesnt work, all of my fuses are fine, and my ground is clean, i dont know what the problem could be, anyone know?

did you use the power wire off of the old radio? are you sure the power wire isn't broken or prayed anywhere? are you sure the ground is still fine?

I'd check all this, and if it still doesn't work, just run a new power wire(?)

there are fuses under the hood too