DIAGNOSIS The optical sensor in the grounds drawer cavity is obstructed or faulty. Coffee oils and fine grounds can coat the sensor window.
FIX Remove the grounds container. Locate the small, clear plastic sensor window on the left interior wall of the cavity. Wipe it completely clean with a dry microfiber cloth. Also, wipe the corresponding spot on the container itself. Reinsert the container firmly until it clicks.
IF THAT DIDN'T WORK The container may not be triggering the mechanical latch that signals it is present. Ensure no coffee grounds are blocking the container's full insertion. Inspect the small plastic tab on the container for damage.
HEADS UP Running the machine without the grounds container properly detected can cause pucks to eject into the drip tray, creating a mess and potential clog.