Unplug the unit for 60 seconds to reset the control board, then plug it back in.
- First cause: A sensor error from a previous preheat cycle. The reset usually clears it.
- Second cause: The door isn't fully closed. Open and firmly close the door until it latches.
- Third cause: You pressed multiple buttons simultaneously or too quickly, confusing the controls. Press the Power button to clear, then start over.
If that didn't work, and 'Err' returns immediately upon power-up, it indicates a fault in the temperature sensor or main control. The fix requires a service technician. Note the exact error code sequence if it changes.
Heads up: Always ensure the crumb tray is correctly inserted before starting any function. A missing tray can sometimes trigger sensor errors.