With the Nuki app you can reset your Nuki Door Sensor to factory settings
To reset your Nuki Door Sensor to factory settings, open the menu (top left) of the Nuki app and tap on "Help". Tap on "Reset Device" and select "Reset Nuki Door Sensor". Now follow the instructions in the Nuki app.
Note: By resetting to factory settings, all data will be irrevocably deleted. After the reset, you can set up your door sensor again.