DIAGNOSIS The frother is not heating. This is typically caused by incorrect assembly preventing proper activation, or the machine is not in 'hot milk' mode.
FIX First, confirm assembly. The frother must be fully clicked into its base on the machine. Second, select the correct function. A short press of the milk button activates 'cold froth'. For hot milk or foam, you must press and hold the milk button for 3 seconds until the light changes to a steady green for 'hot milk' or a blinking green for 'hot foam'.
IF THAT DIDN'T WORK The heating element in the frother base may have failed. Test by ensuring correct mode (steady green light) and feeling the base of the frother unit after 30 seconds of operation. It should be warm to the touch. If it remains cold, the heating unit is defective.
HEADS UP The frother will not heat if the main machine's water tank is empty or if the machine is in descaling lock mode. Check the main machine status first.