LCD not lighting after screen replacement!

Hi,

I bought an iPod touch from eBay without a screen. I separately bought a screen for it and installed it according to professional instructions. I tried to power it up, but no apple logo showed. About 2 min later I pressed the home button and to my surprise siri worked. With a flashlight I noticed the display was working (very dim light) and I could open apps, slide to unlock, etc. However, the display is completely black. I assumed the lcd might not be connected, but even after connecting and reconnecting cables the backlight still doesn't work.

My question is whether this is a screen issue or an iPod hardware issue. The screen and iPod connectors both look perfect in condition.

Any help appreciated!!

Thanks