There are 4 locking tabs on the single serve cup that engage in 4 slots in the base. The slot on the right side has a part in it that slides down when the single serve cup is inserted and rotated into locked position. This activates a switch telling the controls that a single serve cup is attached. If the sliding tab is gummed up with spilt or leaked food, it may stay in the down position after the cup is removed and keep the controls in single serve mode. Clean this sliding mechanism until it moves freely.

Read your owner manual section troubleshooting. However you must test the control board fro defective, but test the main switch for defective use the multimeter for continuity and replace it
God bless you