The answer to 'drain not working' is that there are several common causes, including a clogged drain, a broken or damaged pipe, or a problem with the drain trap. Symptoms may include slow draining water, foul odors, or water backing up in the sink or tub.
Some common solutions for a clogged drain include using a plunger, a drain snake or auger, or a chemical drain cleaner. If the issue is a broken pipe or a problem with the drain trap, you may need to call a professional plumber to diagnose and fix the problem.