The answer to 'drain trap won't flush' is that a clogged or malfunctioning drain trap is the most common cause. The drain trap is the curved section of pipe under your sink or bathtub that is designed to hold a small amount of water, creating a seal that prevents sewer gases from entering your home. If the trap becomes clogged with debris, hair, or other buildup, it can prevent water from draining properly.
Some common symptoms of a drain trap issue include slow draining water, gurgling sounds, or a foul odor coming from the drain. To fix a clogged drain trap, you can try using a plunger or drain snake to clear the blockage. However, if the trap is damaged or the issue persists, it's best to call a professional plumber to diagnose and repair the problem.