Apple Pencil Troubleshooting Tips
If your Apple Pencil is charged and connected to your iPad but still won't respond try checking the tip to make sure it is tightened. The tip of the Apple Pencil will wear down over time, and it is replaceable. This means it can come loose especially if you have been transporting it around with you.
If it is not the tip, try rebooting your iPad by pressing and holding both the Sleep/Wake and Home buttons until you see the Apple logo.
If none of these troubleshooting tips work then your Pencil may be damaged or defective. You can take it to your local Apple retail location to further troubleshoot or request a replacement.