Blue screen repair problem

I have recently repaired an ellipsis 8 tablet. The cracked screen was working before I changed to the new screen. I was careful with everything including and especially the ribbon cable. As far as I know I didn't damage anything. I have done several repairs on several different devices. When the new screen was installed it just shows blue. I reinstalled the old working but cracked screen and now it is doing the same thing. I don't know if I need to order a new ribbon cable or what.