Why wont my iPad charge?

Are you using a genuine Apple cable, or something else? Cables from third-party manufacturers cannot necessarily be relied upon. Likewise, while unusual, a new cable may be faulty.

These support pages should help with troubleshooting battery and charging issues:

Charge and monitor the iPad battery - Apple Support

If your iPad won't charge – Apple Support

Troubleshooting generally requires substitution of the Power Adapter and cable for another known-good item. Be aware that most models of iPad require a Power Adapter rated at 12W or greater to reliably charge. 5W Power Adapters intended for older models of iPhone are inadequate to charge an iPad; if the iPad charges at all, charging will be very slow.

If you continue to experience difficulties when using an appropriate Power Adapter of 12W or greater, you might be well advised to seek assistance directly from from Apple Support - and request a remote diagnostic test. You can contact the Support Team using the Get Support link at top-right of this page. Alternatively, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/gb/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad, Power Adapter and cable(s):

Genius Bar Reservation and Apple Support Options - Apple

… suggesting, in all likelihood, that you may have been misfortunate in having received a defective cable.