Force quitting the app can often reset the app and is a great first step when trying to troubleshoot an issue.
To force quit do the following:
Swipe up from the bottom of the screen and pause in the center of the screen revealing smaller preview icons of all open appsor
Double-click the Home button (on an iPad with a Home button) revealing smaller preview icons of all open appsthen
- To close the App, swipe the App up and off the screen
- for more detailed information visit Apple's help article here: Force Close an App