Please try the following to make sure your Pencil is working correctly:
Make sure its tip is screwed on tightly. A loose tip can render laggy inking or doesn't work at all. Please also try unscrewing the tip and cleaning the metal part.
Check its battery and recharge it if needed. Please see: https://support.apple.com/en-us/HT211019.
Restart your iPad and re-pair your Pencil. Press and hold the iPad's Sleep and Home buttons until the Apple logo appears on the screen. Wait until your iPad has restarted and then pair your Pencil again.
Try it in other apps, like Apple Notes. If you experience similar issues, it is likely that there is a problem with the Pencil itself. We suggest contacting Apple Support for a quick solution.
Check Zoom Accessibility. Please open the Settings app from the Home screen, tap Accessibility, and make sure Zoom is OFF.
Reinstall the app. This worked for a user, but use it as a last resort and back up all your data first.