Is there a way to fix a split keyboard on my iPad?

At bottom-right of the on-screen keyboard you will see a Keyboard key. Touch-and-hold the Keyboard key to expose a menu. Without lifting your finger from the screen, slide your finger to Dock & Merge - then release.

You will now have the full on-screen keyboard visible on the screen - and this will be anchored to the bottom of the screen.

An alternative method to restore the full keyboard is to use two fingers; place one finger on each keyboard segment, then slide your fingers together.

If (when?) the above don’t work, restart the iPad.