Won't turn on, vibrates like crazy

So I replaced a motorola droid maxx 2 screen for a customer recently. The phone worked fine after the replacement was completed. He then comes back a week later telling me the phone will not turn on at all. He left it in his truck for the entire week. Now the display came on one time and then shut off and won't come back on. The phone does continuely vibrate as if it is turning on and off. Nothing I do gets the screen to come back on, but the lcd clearly works because it was on for that 1 minute when he brought it back. I took the phone back apart and all of the connections are good. Please please help.