How do I enable hand off on my iPad?

Try a forced-restart of your iPad and iPhone - 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.

Force Restart iPhone

Force restart iPhone - Apple Support

If the problem persists, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page.

Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:

https://apps.apple.com/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 offer assistance:

Genius Bar Reservation and Apple

Ensure that you have enabled Handoff on all of your devices.

Settings > General > AirPlay & Handoff > Handoff - set to ON

With handoff enabled on all devices, you should be able to transfer FaceTime calls between devices that are (a) in close proximity, and (b) are using the same WiFi network:

Hand off a FaceTime call from your iPad to your other Apple devices - Apple Support

Hand off a FaceTime call from your iPhone to your other Apple devices - Apple Support