Backlight wont display. no drop no water damage

I just put a new screen assembly on my note 2. and within an hour the backlight went out. i did not drop it, there is no water damage. i left the phone in my room to take a shower and i came back and nothing will display. out of memory of knowing where the touch buttons are i began typing a text to see if the whole thing didnt work but it worked fine. i could here myself typing and making screen selection but the backlight just wont illuminate. the screen assembly was knew cost me about 240 after teax and shipping, i just dont know what it could be.