How to add Apple Pencil Gen 1 to the Apple Devices list?

Make sure the Pencil tip is screwed on securely.

Then, try all of the troubleshooting tips in this Apple Website link.

Use Apple Pencil with your iPad or iPad Pro - Apple Support

If still no joy,

The Pencil may be defective.

Bring both the iPad and Pencil into your nearest, “local” Apple Store for diagnosis, testing, evaluation and options, like replacement.

Good Luck!

Apple Pencil is an accessory and not a device in the sense of an actual Mac or iOS device.

What iPad are you using with the Gen 1 Apple Pencil?