For the A2: when facing the unit, the button is located at the bottom left between the front and the body (where the cable goes).
RCM reset – In the event of an RCM error (indicated by a flashing red LED) please press the set-up button twice to reset.
Network set-up mode – Press the set-up button three times in a row to enter set up mode. You will see the amber LED flash. You are now ready to set up your network credentials via your smartphone. You can press the set-up button once to exit this mode. If your unit is not entering set up mode, please make sure that the three presses are in quick succession with no pause in between.
Network credential reset – Press the set-up button five times in a row to wipe your existing network credentials. You should see all LEDs start flashing and then settle to a green LED once completed.
This function can be used if you switch internet provider or get a new router and need to reset the network. At this point, you can enter network set-up mode.