As soon as you are out of the Bluetooth range, the app will no longer be able to receive real-time
temperature readings. Check to see if the Bluetooth LED indicator light on the bottom right of the control is solid blue. If it is blinking, it no longer has a Bluetooth connection.
Bluetooth range can be effected by many factors including interference from other devices, distance, going in/out of buildings and even by the topography of the land. For the best results, make sure you are in direct line of view of the control.
If you are connected via Wi-Fi, check to see if the LED indicator light at the bottom right of the control is purple, or flashing between purple and red. If it is, you have a Wi-Fi connection and you should try closing the app and restarting it as well as rebooting your control.
If the control is solid blue or blinking blue, then you don't have a Wi-Fi connection and you should establish it or reestablish it by going into the main menu of the app and touching "Connect to WiFi". Follow the prompts to login to your account and select your Wi-Fi network.