The answer to 'why is my sewer line won't flush' is that there is likely a blockage or clog in the sewer line. Common causes include tree roots, debris buildup, or a collapsed pipe. Symptoms may include slow draining sinks, gurgling noises, or sewage backup.
If the sewer line is clogged, you may be able to clear it yourself using a plunger, plumber's snake, or chemical drain cleaner. However, if the blockage is severe or the issue is with the main sewer line, it's best to call a professional plumber. They have the tools and expertise to properly diagnose and fix the problem, preventing further damage to your home's plumbing system.