apple pencil not working

Having forgotten the Pencil, detach it from the iPad - force restart the iPad - and then attempt to re-pair.

To force-restart the iPad - press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

This support page may be helpful with pairing and use of the Pencil with your iPad:

Connect Apple Pencil with your iPad - Apple Support

If you continue to experience difficulties, here is one of the better troubleshooting guides:

https://appletoolbox.com/apple-pencil-not-working-heres-our-troubleshooting-guide/

Perhaps exploring the obvious here, but have you tried forgetting the Pencil before attempting to re-pair your Pencil with iPad?

1. On your iPad or iPad Pro, go to Settings > Bluetooth.
2. Find your Apple Pencil under My Devices and tap the blue i button.
3. Tap Forget This Device.

Prior to this issue, when was the last time your Pencil was charged up and used with your iPad?

Did the Pencil EVER lay around completely dormant for any extended period of time without any charging?