Suddenly my 3rd unit's LED went yellow and has been like this for more than 2 days, and it cannot be reached from the app. I tried moving it close to the main unit, connected it instead of the main unit, used the power supply from one of the other units, reset it many times (1s, 5s and 30s). I deleted it from the app and cannot add it as it cannot be reached nor does the led every become blue for reconfiguring. Every so often the led blinks red, and then it goes back to solid yellow. Short of returning it (I bought it online so I am trying to avoid this) is there anything that I am missing ? (my other two units remain working fine; was bought as a pack of three)

Thank you