Mower won't start not a sound

Start by testing for voltage at the battery. Check it again while attempting to start. If the voltages are close, your battery is probably ok. If voltage while attempting to start is much lower than the battery at rest voltage, then the battery is suspect. Most places that sell batteries, will test them for free. If the battery is good, check voltage at both sides of the solenoid. One should be the same as the battery and one should have nothing. Try starting again while checking the side that had nothing before. You should get close to the same as the battery voltage. If not, the solenoid could be your problem. Any of the safety switches or the start switch could also be faulty. It could be any combination of things from here, so a good knowledge of these engine/mower systems will be necessary. It would probably be a good idea to take it to a small engine repair shop.