Let me guess when you removed the LCD, you didn't realize that it was tapped down on the home button end and you flexed the screen when removing it. The LCD is pretty fragile, did you follow a guide on here to repair? I am assuming your LCD was fine before repair. So you either cracked it some how when removing or its an defective LCD. You can also try blowing out the connectors with canned air as you might have some small debree on it. Also make sure there isn't any damage on the connectors (on the LCD cable and board) if you find damage you know were to point to.

I have replaced hundreds of these, the more than likely causes are: (1)Glass isn't sitting properly or LCD is fastened down all the way. Ensure that that LCD is screwed down all the way and that the front panel/digitzer is set down all the way - if it isn't you probably have corner or side damage or debris left behind like glass or glue, that is preventing it from sitting down where it needs to be. Fixing damaged corners or sides can be tricky, I use the G-Tool to reshape damaged areas. Also try not to destroy/remove the bezel that is mounted to the frame it is an aid for the glass to sit properly on top of the iPad. You can remove the bezel if needed to reshape, just make sure you put it back down and glue/sticky tape it back to the frame. (2) Check your connection cable for any slight tears. Check the end of cable where it mounts to the board make sure it free off debris and not damaged. Also make sure that the board is clean where you are mounting the cable/ribbon into, use canned air if needed to blow...