Why is my screen blank after power button repair?

Hello!!!

I carried out a power button repair on my iphone to which I thought had been a success. Prior to putting the phone back together the power button was clicking perfectly, after assembling the phone to which I have a sharp eye and nothing was missing or not put back as it should of been but the screen is now not working. The backlight is functioning, and I can hear the power button working etc, but for some reason the screen is not displaying.

Any thoughts or advice would be greatly appreciated.

Regards