The answer to 'my circuit breaker won't turn on' is that there are several common causes, including a tripped breaker, a short circuit, or a problem with the electrical panel. Symptoms may include no power to certain outlets or appliances, flickering lights, or the circuit breaker repeatedly tripping.
If the circuit breaker won't turn on, first check for any obvious signs of a problem like scorch marks or a burning smell. Then, try resetting the breaker by fully turning it off and then back on. If it still won't stay on, there may be an underlying electrical issue that requires troubleshooting. For simple problems, you may be able to resolve it yourself, but for more complex issues or anything involving the main electrical panel, it's best to call a licensed electrician.