Do not reset the sensor via the reset button.
Do not reset the hub.
Make sure your hub is online via the Sengled Home app by pulling down on the "Home" page to refresh.
In most cases, a sensor that shows offline will still function and record the open/close triggers.
If the sensor is offline, trigger the sensor by parting the two parts—i.e. open the door, window, drawer or the object to which the sensor is attached. Leave the two parts of the sensor apart for at least three seconds. Then, you can return the sensor to the closed position.
From here, to refresh the Sengled Home app, close the Sengled Home app by viewing all the running apps on your phone and swipe the Sengled Home app away.
Now, wait at least 60 second. Then, open the Sengled Home app up again and see if the sensor is still offline.
If the sensor is still offline, remove the battery completely and reinsert the battery.
After that, close your Sengled Home app, wait at least 60 seconds, and reopen the Sengled Home app. See if the sensor is still offline.
If the sensor remain offline after all of the aforementioned steps, we would recommend deleting the sensor, resetting it via the reset button and adding it back as a new sensor.
The following link explains how to reset the sensor via the reset button: https://support.sengled.com/hc/en-us/articles/360024362854-How-Do-I-Reset-the-Smart-Sensor-