The red light in the control button should blink after you hold the button down for at least 3 seconds. If it doesn’t, it might mean that the milk or water in the bottle is already at the correct temperature.
Another possible reason could be that the food is too cold. If the temperature is 0°C or below, the warmer will not start. You cannot heat frozen milk or water in the S-bottle warmer; they need to be thawed first. Food from the refrigerator typically has an average temperature of about 6°C.
If the red light comes on briefly and then turns off immediately, this may indicate a malfunction. In this case, please contact Difrax Customer Service via the contact form.