Reboot your device by holding the power button down for a few seconds. The device should prompt you to complete the shutdown. Turn the device back on.
If rebooting doesn't fix the problem, try deleting the app, then reboot the device as stated above. Download it again from the App Store. You will not be charged a second time. This will clear errors that may have occurred during your initial installation.
If you require additional assistance, please contact us.