Push the drain line.
Dishwasher air vent leaking water.
The air gap is just that a gap of air in the dishwasher drain line so dirty water can not be forced up out of the sink and into the dishwasher.
Without the air gap dishwashers must siphon out all of its water or pull dirty wastewater into the dishwasher to drain.
Tap the screwdriver handle with a mallet to remove the plug.
The dishwasher refuses to push more water through the blocked pipe and therefore water has to escape through other exits such as the air vent pipe.
Air gap problems are usually caused by a leak or a clog in the drain hose.
The two never meet they re separated by a literal gap of air.
If the plug is still in the disposal the water draining from the dishwasher has nowhere to go but out the air gap.
A problem with the air gap can cause the dishwasher not to drain at all or it can cause water to leak into the sink or onto the countertop.
When the gap leaks it is normally due to a kink or blockage in the tube from the air gap to the tail piece drain line below the sink.