Replaced LCD & digitizer, screen still blank, any advice?

I replaced the digitizer via using a heatgun to remove it from the adhesive, and placing the new one in securing it with a tiny dab of superglue in the spot where the previous adhesive had come off and re-using the rest of the intact adhesive; works a treat.

I replaced the LCD screen as it was cracked, once I put the phone back together, when I fire it up, the backlight comes on as does the start-up audio/vibration but there's no actual picture, just an illuminated black screen.

The circuit board seems to be in working condition, and I checked the digitizer and LCD connections to the circuit board, and they're both secure.

Any idea what the problem is?

It's for a HTC desire C, however it's pretty much applicable to any smartphone