Screen replacement worked for 1 day then died

Hi everyone.

I have a iphone 4s and screen cracked ages ago decided to repair it finally.

bought a replacement screen and it arrived, i opened up the phone and tried to fit it and turns out they sent me a iphone 4 one not 4s so it didnt fit, i tried to connect the flex cables anyway and it didnt work that well.

anyway next day bought another screen for 4s this time and got it fitted. it turned on and worked well for the rest of the day and then at night it turned off and hasnt come back on since.

I have charged it and the sound toggle on the left top makes the phone vibrate and i can call it and it will ring.

at a few times when i played around with the charger and stuff the screen lit up for a while, like a white hazy border inside the screen but nothing to resemble the wallpeper or homescreen.

the backlight doesnt seem to come on at all but i think i heard the keyboard type once but havnt been able to confirm since the screen isnt working..

i can disassemble it and reassemble it but i dont think it will help.

i have tried to undo and re seat the lcd tabs (two of them) but doesnt make a difference.

do you guys think it might be the connection on the motherboard thats the problem and not the screen?