The G2 is a miserable screen to replace. So many problems and defective replacement screens.
The G2 likes to go into deep hibernation when you take it apart. I have no idea why, but I would try a soft reset first. That works sometimes. Then we can take it from there if that doesn't work.
I believe for the G2 you hold the volume up and power button together for about 10 seconds to soft reset. (have it plugged into charger while you do this)