What are you asking. Well actually you aren't asking anything. You made two different statements.
The iPad was not designed to charge efficiently from a computer USB port. It will recharge from a high powered 2.0 USB port of the computer is awake and the iPad is asleep but it can take quite a while to recharge. You will get the "not charging" message but it may still be trickle charging, If the USB port does not supply enough power the battery will not charge.
Is the iPad being recognized in iTunes? Saying prior syncing worked well does tell us anything at all. If you need help, provide some specific details, please.