Radio power issue

I have recently added an amp and new speakers to my 96 monte carlo. I ran all the wires and made the proper connections to the amp. I ran into a major problem with the headunit though. A few months ago i installed an aftermarket headunit which worked great. After i ran all the wires for the new system in teh car i plugged the headunit back in and turn the car on and i get no power at all to the headunit. Every other power unit in the car works, windows locks ect.... I have checked all the fuses in the passenger door. I also put the stock headunit back in to see if it was the headunits problem. At this point i am lost as to what is wrong and why i am not getting power to my headunit.. If anyone can offer advise it would be greatly appreciated.

thank you
Nick