Diagnosis
The float sensor is stuck or fouled by mineral deposits, so it can't register the correct water level.
How to Fix It
Manually unstick the float. Unplug, remove the water tank, and locate the small white float inside the unit's water reservoir. Gently move it up and down its post several times to free it.
If That Didn't Work
Mineral scale might be insulating the sensor's contacts. Descale the entire internal water system with a food-safe citric acid solution or undiluted white vinegar run through a cycle.
Heads Up
Never use force on the float assembly. If it's physically broken, the unit won't work. The sensor is a common failure point if it's forced.