The answer to 'why is my sump pump won't flush' is that there are several common causes, including a clogged impeller, a faulty check valve, or a problem with the float switch. Symptoms may include the sump pump running continuously, the pump not turning on, or water not draining properly.
Some potential solutions include cleaning the impeller, replacing the check valve, or checking the float switch for proper operation. However, if you're not comfortable troubleshooting the sump pump yourself, it's best to call a professional plumber to diagnose and fix the issue.