Apple Pencil 1st Generation is now junk !.

[Greenman]

My Apple Pencil 1st Gen only used twice is now a £120.00 piece of junk, how you say, it was put in a draw for a while and for got about, when take out again for use the battery was found to be flat down to 3%, when it reaches that level it will not take any charge no matter how hard you try, the battery can not be replaced as they are a fully sealed unit, if you check out YouTube where's one or two people who have cut them open, you'll find a steel sleeve which houses the slim Lithium battery, there's 1 chap who has been able to replace it and 3D printed a new outer cover for it.
So if you have one make damed sure you keep it charged up, and I'd say that go's for the new second Gen too

 

[Raz0rEdge]

How long was it left to discharge? You might want to leave it plugged in for an extended period of time to see if it can overcome the deep discharge.

 

[JohnCL]

I have seen people find success with your issue by plugging the pencil into the iPad and then hard booting the device with the pencil still plugged in. Worth a shot...