Hello, A red LED on the switching unit indicates a loss of communication with the control unit. Reset the switching unit, put it into pairing mode and power it up in the appropriate configuration. If communication drops out again after a while, it looks like a problem with the wireless signal range - check the location of the switching unit (if it is not located somewhere behind the boiler or next to metal objects), or move the switching unit to a location with a better signal. For example, sometimes it is necessary to move the switching unit from the basement to the ground floor (and to stretch the cable to the boiler accordingly).