Internet connection.

If you didn't try to connect that iPad to a different network, I can't give you any further suggestions, except trying a reset of network settings in Settings>General>Reset>Reset Network Settings, bearing in mind that this procedure also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before, but NO other data is affected.

If the issue still persists, contact Apple Support directly, using this link:--> Get Support

Regards and best of luck.

Giulio

Have you tried to connect your iPad to a different wifi network (a friend's one, or in public place, or at an Apple Store or AASP)?

It if works, the problem is with your modem-router (or with your ISP provider).

Regards

Giulio

Have you already tried to restart your modem-router, waiting for its complete autoconfiguration?