Coffee Machine Milk Not Frothing or Coming Out Flat

What it
usually means.

An automatic milk system pulls milk up a thin tube with steam, mixes in a measured amount of air at a tiny intake, and heats and foams it on the way to the spout. Everything in that path is small, so dried milk blocks it quickly. The single most common cause of flat foam is a milk tube and frother not rinsed after the last drink, or a milk cleaning cycle skipped for a few days. The milk itself counts too: foam forms best from cold milk straight from the refrigerator, and warm milk, some plant milks and ultra-pasteurized milk all foam less. A frother put back with a part missing or the air intake turned to the wrong setting gives only hot milk. On the machine's side, scale in the steam path weakens the steam, a valve in the milk circuit can stick, and on a manual espresso machine a steam wand with a clogged tip spits instead of foaming. Most of the list is cleaning and use, and a technician is needed only when the clean circuit still fails.