In most cases, the Wi-Fi connection is lost. Check your device settings under the Settings icon -> Wifi. Sign in to your Wi-Fi network again, then go back to Singa.
Note that sometimes your device may require resetting your network connections if the connection is poor. Settings -> General -> Reset -> Reset Network Settings. After that, follow the steps above to log in again.
Did this help? If not, contact firstname.lastname@example.org or chat with us through the Singa application at Support.