The teeny, tiny battery in your Apple Pencil has failed and your Apple Pencil is dead.
The Apple Pencil cannot be repaired, at all, without actually destroying it.
With no more warranty period left, you will need to purchase a new Apple Pencil.
Here is some info about the Apple Pencil you need to know.
FYI and something Apple never divulges to it potential iPad/iPad Pro/Apple Pencil customers/users unless the potential customer/user is smart enough to ask about.
Due to the “always on and active/standby” nature of the Apple Pencil and, also, due to its very tiny rechargeable Li-
ion battery (smaller than the eraser head on a REAL wooden pencil), the Apple Pencil needs to be constantly
charged up to some significant charge level ALL THE TIME, even when not using the Pencil for prolonged
periods of time.
The Apple Pencil needs to be kept charged to a minimum of 5-10% ALL THE TIME!
If the Apple Pencil battery is allowed to drain down to 0% and allowed to stay in that flat condition for more than a few weeks, or so, OR EVEN LONGER, that very tiny little Li-ion battery is too small to keep at a 0% state for a long period of time and it will fail and the Apple Pencil will be dead and you may have to “pop” for another $99 Apple Pencil, once again!
You need to keep your Apple Pencil charged all the time, even if it is only to 10%-15% charge. It must keep some
charge level in that tiny Lithium-ion battery at all times!
Best of Luck to You!