My Apple Pencil has been attached to my iPad for hours yet still on 0 charge

These support pages may be helpful with pairing and use of the Pencil with your iPad:

Connect Apple Pencil with your iPad - Apple Support

Charge your Apple Pencil and check the battery - 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/

If you attempted to pair the Pencil with your iPad - and have followed all the advice given - then your Apple Pencil may be exhibiting symptoms of a dead battery - that will not accept or hold any charge.

The tiny internal Li-ion battery is susceptible to permanent/irreversible damage through being left discharged for long periods. Even some “new” pencils can exhibit signs of failure out-of-the-box if they are “old stock”. It is essential that if you have an Apple Pencil that you charge it regularly - whether used or not - so as to protect the battery from deep-discharge.

Do not allow a pencil to remain in low-charge state for any period of time - as the internal battery will fail, rendering the Pencil useless. Setting aside an unused Pencil, for extended periods, is a recipe for premature death of the Pencil battery. A second generation Pencil should be docked with the iPad whenever is it not being actively used - as doing so will keep the Pencil optimally charged and protected from battery damage.

If the Pencil Battery has failed, the only remedy is to replace the Pencil. If the battery has failed and your pencil is within its one-year warranty, you should look to having it replaced by your retailer or at an Apple Store.

I hope this information proves to be helpful in both diagnosing and resolving the problem.

Start here >>> Charge your Apple Pencil and check the battery - Apple Support

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