ipad troubleshooting - restarting apps
The next step is to press and hold any app that shows up at the bottom of the screen until they wiggle and show a red minus sign at the top-left of each icon. Tap the red minus sign of the app you want to completely close.
Click the home button once to get back to the main screen then re-open your app.
Note: While this works most of the time, some issues require you to delete the app and reinstall it.