It's possible that you just need to temporarily restore Bluetooth functionality to the app.
First, check to see that your mobile device's Bluetooth is ON.
Next, check to see if the Bluetooth is on in the SensorPush app as well. Here's how:
1.) Open the app, and from the main screen (the screen with the word "Devices" at the top) select the button in the top left to open app settings.
2.) Once in app settings you'll notice a section called "Configuration" with a switch for Bluetooth. Switch it ON.
Then, bring the phone into close range of the sensors (e.g. same room). This should help wake them up and put the sensor device fully into its regular power mode.
One last thing to try is to re-add the sensor to the app essentially like it's a new sensor. The app will likely produce an error and state "Sensor already paired as..." but this will also re-activate the sensor.
If none of the above works, please contact us at firstname.lastname@example.org