iPad Air Magic Keyboards trackpad is not working

Hard to know what you've tried unless you tell us?

The first thing I'd do is Force Restart your iPad (something recommended after every iPadOS update:

• Press and quickly release volume up button
• Then press and quickly release volume down button
• Then immediately press and keep holding the top power button (keep holding past the swipe to power off) until the Apple Logo appears, then let go
• Once you sign back in with passcode, see if normal trackpad operation resumes

OK.....See this link and go into the trackpad settings on your iPad and see if adjusting anything helps --> Set up and use Magic Keyboard for iPad - Apple Support