On newer iOS versions, Stage Manager can interfere with opening the tab definitions.
To prevent this issue, use one of the two methods below to disable Stage Manager.
Method 1: Open Control Center
Swipe down from the top-right corner of your iPad screen.
Tap the Stage Manager icon (a rectangle overlapping another).
Method 2: Disable Stage Manager via Settings
Go to Settings > Multitasking & Gestures > select 'Off' under Multitasking.