iPad Says "not charging"

Try to use a different charger.

Also, try to reset your device. This won't delete your data stored on the phone.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

https://support.apple.com/en-us/HT201559

If this does not help, restore your device to factory settings. Note that this will erase the data from your device.

Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.

Take a look at this support article:

Charge the battery in your iPad - Apple Support

Also, I think this thread may help:

getting message: not charging

You will see that message when:

1. the Cable you are using is not a certified cable. Use a good name brand cable or an Apple cable.

2. The charger you are using does not provide the amount of power expected by the iPad. Use the charger that came with your iPad.