Why is Screen only showing backlight?

I am working on a Mini 2 and doing a LCD And Glass replacement. This was/is my first mini 2 ive taken apart so i wanted to test my work before sealing it back together. It boots fine, i see the apple logo a can navigate the OS once its fully boots. But once i let it sleep or even tap the power button then try to turn it back on, i only get a backlight. I know it is functioning still because i can hear the charge sound from plugging it in. Also pressing the power button till wakes and sleeps the lcd as it should, but its only getting a backlight.

I had a theory that it might be some silly apple sensor stopping it from working properly till its fully sealed back up, but i cant find anything that supports that.

Thank you for taking your time to read and help.