Get a can of dry, compressed air. Clean any dust out of your board.
With that done, take your LCD off the digitizer(6 tiny little screws). Make sure you are on a static pad or have grounded out, and run your finger along the spot where the digitizer ribbon is laminated to the digitizer. Is it fully attached ? If not, you know your problem.
If so, check to make sure the digitizer board is connected to the mother board. You will see a tiny cable running from the digitizer board to the mother board. You might disconnect it, blow it off, and reconnect it.
Finally, as bad as this sounds: It is a trial and error process to get the digitizer connected properly, unless you are very gifted or do this all the time. It took me probably 6 or 8 times to get it to seat properly, go all the way in, and connect.
I kid you not. I know 6 times, but probably 8 times. Don't put it all the way back together until you've got it working.
It will seem like it is in and seated, the screen will light up, but you will have dead spots or no response at all.
I forced it into recovery mode, re-installed WebOS, and then did what I told you above.
Keep working the digitizer ribbon to where it installs on the digitizer board. Be careful, be rested, be patient, and keep trying.
It finally worked on mine and now it is like having an old friend back. And other than the rear case scratches and case cracks, it is like new or better than new.