This is usually caused by a problem with your Internet connection or the settings on your phone.
Please try these steps to fix your connection:
1. Reboot your phone (power off, power on).
2. Update the app to the latest version. Go to Google Play on your Android.
3. Turn Airplane mode on and off (Android Settings > Wireless & networks > More... > Airplane mode).
4. Make sure that data is enabled (Android Settings > Data usage > Cellular data).
5. Go to Android Settings > Data usage > Menu Button > make sure Restrict background data is unchecked.
6. Turn Wi-Fi off and back on (Android Settings > Wi-Fi).
7. Try connecting to different Wi-Fi hotspots.
8. If you are often connected to Wi-Fi, check your Wi-Fi sleep policy (Android Settings > Wi-Fi > Menu Button > Advanced > Keep Wi-Fi on during sleep) and make sure it is set to "Always."
9. Reboot your Wi-Fi Router.
10. Delete and reinstall the app.
11. Upgrade your Android OS to the latest version available for your phone.