Three causes, in the order they happen.
The tank is not seated
Water tanks push onto a spring-loaded valve. If the tank is a millimetre short, the valve stays shut and the machine sees no water.
Take it out and push it firmly back until it clicks. This is the answer most of the time.
An airlock
After running dry, the pump cannot prime — it is trying to push air. The machine reports no water because none is arriving.
Open the steam wand or the hot-water tap and run the pump for ten to twenty seconds. You will hear the note change when water arrives.
The sensor is fouled
Machines detect water with a float, a magnet or a conductivity probe. Scale and residue stop floats moving and confuse probes.
Empty the tank, wipe the sensor area, and check that any float moves freely.
The distilled water trap
Conductivity sensors need dissolved minerals to detect water at all. Fill a machine with distilled or reverse-osmosis water and it may genuinely report an empty tank while full.
That is one more reason not to use distilled water on its own.
If none of it works
Unplug for five minutes. A surprising number of these are transient states that a power cycle clears.
Last reviewed 8 August 2026