I have had the same problem as you. I am on my third screen, and I am about to send this one back and just get a full refund.
The first one was cracked, The second one got no power, and this one has the same problem that you have.... I hope someone can answer this post, beucase I don't know what to do!? I checked all the cables, etc, re-installed, opened the screen and made sure the ribbons were all connected, and I'm getting nothing.
I think the touch panel is just shot.
I'm learning that lilliput is ****, unfortunately!