Wifi not working

As described, you iPad may have a hardware issue - that would certainly benefit from test and assessment.

Given that your iPad cannot join a WiFi network, remote diagnostics are not possible. As such, you would be best advised to visit the 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. If repair is required, you’ll be in the best possible place to explore your available options:

Genius Bar Reservation and Apple Support Options - Apple

Begin with forced restart of your iPad - as this will often clear an isolated software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.