iPad does not ring when I receive a call on my iPhone

This may suggest that your WiFi network is not forwarding traffic between network clients.

For your WiFi network, have you mistakenly enabled any privacy features - such a PSPF or other privacy feature. To be clear, this will be a setting on your WiFi Router - or if used, any WiFi Access Points or network extenders.

If everything was previously working - and you have made no changes to your WiFi network or its configuration, a restart of your network components may resolve the problem. You’ll need to restart your network devices in the correct order. Assuming that you WiFi Router provides DNS services for your network, restart devices in this order - allowing time for devices to fully boot/restart prior to restarting other devices:

• WiFi Router
• Upstream wired Network Switch(es)
• WiFi Access Points / Network Extenders
• Other fixed infrastructure devices - such as Printers
• Client devices

Restarting your iPad, after restarting other devices in the correct sequence, is most simply achieved by a forced-restart of the iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.