Sometimes the easiest way to fix an issue with the App is to update it, or by deleting it and reinstalling the App.
You will NOT lose any data, as it is all stored on our servers.
Check the App Store for updates, and click on 'update' if you don't have the automatic update downloads. It is located in the App Store, under the 'Updates' tab.
Reboot your phone by shutting it down and restarting your phone.