Are you having difficulties with one or two specific Apps, or all Apps - including, for example, Calendar, Reminders and Notes?
If the issue affects all Apps, perform a forced-restart of the iPad:
- On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
- On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.
If instead the problem only affects specific Apps, uninstall the App - restart the iPad as described above - then reinstall the App from the Apple App Store.