Not Charging even after battery and charging port replacement.

Something I've never seen before. A customer came in to my shop today saying her phone wouldn't charge at all. Nothing would come on the screen when plugged in. My first thought was battery is bad or charging port. Replaced both, now it will turn on by pressing the power button. All seemed well until I tried charging again and it wouldn't charge. Tried different cable, still no luck. Phone WILL turn on if cord is connected. Computer will not recognize either. Any solutions?