Remove the back plate by using the included tool or a wedge to click it off. Press and hold the reset button inside the device for +- 5 seconds (until the blue light starts blinking). After this the device will automatically join, but the interview process may not finish. If that happens, keep doing short presses to the reset button to keep the light flashing, until the interview process finishes successfully.
Troubleshooting: device stops sending messages/disconnects from network Since Xiaomi devices do not fully comply to the Zigbee standard, it sometimes happens that they disconnect from the network. Most of the times this happens because of the following reasons:
Device has a weak signal, you can see the signal quality in the published messages as linkquality. A linkquality < 20 is considered weak. Low battery voltage, this can even happen when the battery still appears full. Try a different battery. The device is connected through a router which cannot deal with Xiaomi devices. This is known to happen devices from: Centralite, General Electric, Iris, Ledvance, Legrand, OSRAM, Sylvania, SmartThings, Securifi. A possible solution is to connect the device directly to the central coordinator by pushing the reset button while being physically close to it.