You can try to close other apps running on your device and relaunching the app. We also suggest that you check that your Internet connection is functioning properly. All of our apps require an Internet connection to run.
If you are still having problems, please contact us at firstname.lastname@example.org to let us know what the issue is and which device you’re seeing it on, then we’ll do our best to help.
Note that we normally receive anonymous crash reports when our apps fail, so we may already be working on a fix.