Screen will not turn on.

The Blue light comes on solid, the red light occasionally appears depending on the set of buttons that are held down during the attempted power up. The phone gets warm and I have taken the back glass and middle housing off to check all connectors. All seemed to be secure. I did release them all and attempted to purge power from the phone. Still nothing. When I get the phone to have no lights on, and then plug it in, the blue light comes on solid. Any ideas? Client says the phone has not been dropped and there is no sign of water damage.