Update 15

Please follow the steps at If your iPhone, iPad or iPod touch won’t connect to a Wi-Fi network – Apple Support to help troubleshoot this issue.

You may need to reset your network settings (Settings >, General,> Reset > Reset Network Settings), this will not erase any data from your phone however you will need to log back in to any WiFi Networks you use, and it will also reset VPN settings.

Got VPN?

Try disabling it or, temporarily deleting it from your iPad.

Re-establish your WiFi connection.

If you choose, re-download the VPN and re-enable it and see if your WiFi connection stays stable.