Can not get the white screen to go

Hi Folks

i really hope you can help.

i have an ipod touch 4th gen, i have changed the screen and it was working for a short time after. like a few minutes. while i had it apart.

but i switched the ipod off put it all back together and i am now getting the white screen.

the sound is still working and so are all of the buttons, i can hear the lock and unlock sounds and i can turn on voiceover with a triple click and the volume on that will go up and down but i just cant get rid of the white screen.

i have tried all of the fixes i can find on here and on google but nothing seems to be working.

i have tried the screen on another ipod 4th gen and it works on that without error.

pls help