Have you enabled the Scribble feature? This feature uses a different mini-keyboard that does not respond to the two-finger zoom or pinch gestures.
Settings > Apple Pencil > Scribble - set to OFF
After disabling* Scribble, you may need to force-restart your iPad:
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:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.
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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.
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(*) If Scribble is currently disabled in iPad settings, set to ON - then close the settings App and perform a forced restart. After restarting, again set to OFF and again perform a restart.
Otherwise, to restore the new Floating Keyboard to the normal on-screen keyboard presentation, use the two-finger “zoom” gesture (i.e., the reverse of the two-finger “pinch”).
If the Split Keyboard is restored instead of the full on-screen keyboard, you can either use two fingers (one on each of the two half-keyboards) and swipe the two halves together - or touch-and-hold the “keyboard” key, then slide your finger to the Merge & Dock option and release.
Use the floating keyboard on your iPad – Apple Support
Split and move the keyboard on your iPad – Apple Support