The answer to 'why is my garbage disposal won't flush' is that a clogged or jammed garbage disposal is the most common cause. This can happen when food, debris, or foreign objects get stuck in the disposal, preventing proper drainage and flushing.
Some common symptoms include the disposal making a humming noise but not spinning, water backing up in the sink, or a foul odor coming from the drain. To troubleshoot, first try resetting the disposal by pressing the reset button on the bottom. If that doesn't work, you may need to manually clear a jam or call a professional plumber.