Why is my phone showing a blank display

yesterday i purchased a new screen and installed it on my phone however, it is showing a blank display. when someone calls on my phone it rings but i cant answer the phone call as the screen is not sensing my touch either. however i can here the ringtone, the notification tune, the side senser vibrates when i place my finger on it. the phone technician that helped me replace the screen said its a power failure and that my phone has an issue with the motherboard but i dont think so. what could be the problem please