I chatted with someone at HP and they helped me find a soloution. If your HP touchpad is not charging, it may be that you have to reset your plugin i.e. the cylinder that you plug into the wall. To reset it, unplug the cylinder from the outlet, remove the usb cable. You then twist the end of the cylinder with the prongs counter clockwise, then you twist it back to its original position. You don't have to twist it that far until you reach resistance in either direction.
There you have just reset your plugin, so plug it in directly to a wall outlet and hopefully you will be able to charge your touchpad. The customer service rep said to leave it plugged in for 2 hours to see if it worked or to get back in touch with them...but almost immediately I saw a white light down by the home key that pulsed back and forth.
Other things I tried.
I tried plugging the touchpad into my computer before trying this and I don't think you get enough power if your battery has completely drained. I also tried holding down the power button and home button. One of the first things the HP person asked me to try is to hold the power button down and press the home button 15 times. This did not work for me in this case, but may help someone out there.
Hope this helps some people resolve there problems.