DIAGNOSIS E-1 indicates a door switch problem. The microwave's safety system isn't detecting that the door is properly and fully closed. It could be a faulty switch, something blocking the door latch, or an alignment issue.
FIX First, power cycle the microwave by unplugging it for 30 seconds. Then, thoroughly inspect the door. Look for any crumbs, grease, or debris in the latch area (the hook on the door) and the corresponding strike plate inside the cabinet opening. Clean it with a dry cloth. Open and close the door firmly several times, listening for a distinct 'click'. Ensure nothing on your stove below is obstructing the door from swinging fully open or closed.
IF THAT DIDN'T WORK If the error persists, one of the three door interlock switches is likely defective. Diagnosing which one requires a multimeter and accessing the switch panel behind the control console, which is a repair best left to a technician due to the high-voltage risks inside.
HEADS UP Never try to operate the microwave with an E-1 error or by bypassing the door switches. The interlock system is a critical safety feature that prevents the magnetron from operating with the door open.