Get a DMM and check if the stock power wire and/or ignition wire are indeed powering up at around 12V. If that's ok.. then re check your wiring.. did you perhaps miswire your ground and power cables? If you are not using your stock harness ground, ids the ground you have chosen sanded and clearly secured?

If that's fine, then check ALL fuses pertaining to that area (some HU's have fuses internally or externally..refer to your manual for more on this)... good luck!