cannot pair apple pencil on ipad

Your second generation Apple Pencil is only compatible with the 2018/2020 models of iPad Pro - and the new 2020 (fourth generation) iPad Air.

The iPad3 is not compatible with either version of the Apple Pencil. A third generation iPad Air (i.e., iPad Air3) is compatible with a first generation Apple Pencil.

Here is the full compatibility list for Apple Pencil and iPad:

Apple Pencil (2nd generation)

You can use Apple Pencil (2nd generation) with these iPad models: 

• iPad Pro 12.9-inch (3rd generation) and later
• iPad Pro 11-inch (1st generation) and later
• iPad Air (4th generation)

Apple Pencil (1st generation)

You can use Apple Pencil (1st generation) with these iPad models:

• iPad Pro 12.9-inch (1st or 2nd generation)
• iPad Pro 10.5-inch
• iPad Pro 9.7-inch
• iPad Air (3rd generation)
• iPad (7th generation)
• iPad (6th generation)
• iPad mini (5th generation)

Not sure which iPad you have? Identify your iPad model.

I hope this clarification is helpful - if only in understanding the limitations of your Apple Pencil and iPad.

Not compatible.