You may have gotten an Pencil that may have been sitting in a box for many months.
This is a long-term known issue/flaw with ANY version of the Pencil.
Pencils cannot be stored for any prolonged period of time and NOT keep them charged up to some level.
If your Pencil/s sat around unused or unopened and not kept charged up for more than a few weeks, or so, OR
EVEN LONGER, then the battery in your Pencil may have failed and is dead and you will have to purchase another
brand new Pencil or get, if still under warranty, a free replacement Pencil from Apple.
Sorry.
And it looks like some things about the Pencil have NOT changed in the new version 2 model, either.
FYI and something Apple will never, EVER divulge to it potential iPad Pro/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 Pencil and, also, due to its very tiny rechargeable Li-
ion battery ( smaller than the eraser head on a REAL wooden pencil ), the 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.
Apple/Apple Stores or Apple employees will never, ever, mention/divulge this long term issue/flaw of the Pencil.
The Pencil needs to be kept charged to a minimum of 5-10%, OR GREATER, all the time.
If the 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 Pencil will be dead and you may have to “pop” for another $99/$129 Pencil, once again!
Apple only has a one-year warranty on any Apple accessory items.
You need to keep your 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!
One last ditch thing you can try is to plug the Pencil's Lightning connector into the iPad.
Then, try a simple hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.
OR
Try the new hard reset procedure for the 2018/2020 iPad Pro/iPad Air 4 models without a Home button.
1. Press and release the volume UP button.
2. Then immediately press and release the volume DOWN button.
3. Then, press and hold the Power button at the top. You will see the Slide to Power off button, but keep on holding down the Power button until you see the Apple logo, then let it go.
Once you have performed all the steps, wait for a few seconds and your iPad Pro will boot up completely to the iPad Pro’s Lock screen.
See if the Pencil starts charging then, when it reaches a sufficient charge, like over 15%, or so, or more, disconnect the Pencil and reconnect it to see if it Bluetooth pairs.
If it does pair, try using it.
Someone else posted another possible idea/solution that you can try before completely giving up on your Pencil.
Try heating up your Pencil using a hair dryer on its highest setting for 5-15 minutes, or so.
Do not get the hair dryer heat too close to the Pencil.
Or try leaving it near an active home heating register, where you live, for 10-15 minutes, or so.
See if this will revive the Pencil battery, or not.
If still no joy, your Pencil is definitely dead.
Sorry and Best of Luck to You!
