A persistent red light almost always traces back to one of the machine's physical sensors — drip tray, water tank, or coffee grounds container — rather than an internal fault.

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01Drip tray not fully seated

The drip tray has a float indicator and a physical sensor contact point. Remove it completely, empty it if full, dry the contact area, and reinsert firmly until it sits flush — a slightly misaligned tray is the single most common cause of a stuck red light.

02Coffee grounds container full or not detected

The internal grounds container (for used coffee pucks, on models with a built-in grinder) has its own sensor. Empty it even if it doesn't look full — grounds can pack down and fool the sensor into thinking it's not fully seated.

03Water tank sensor misreading

Wipe the contact points on both the tank and the machine body where they meet — mineral deposits or moisture here can interfere with the sensor reading correctly, even with a full, properly seated tank.

Quick check Remove and reseat all three components (drip tray, grounds container, water tank) in sequence, drying contact points as you go. This resolves the vast majority of persistent light issues without any parts needing replacement.
If it persists after this A red light that won't clear despite everything being clean, empty, and correctly seated may indicate a failing sensor itself, which typically needs professional service — check De'Longhi's support center.