1. Check the starter relay. The starter relay is responsible for sending power from the battery to the starter. If the starter relay is faulty, it can prevent the starter from engaging.
2. Check the ignition switch. The ignition switch is responsible for sending a signal to the starter relay to start the engine. If the ignition switch is faulty, it can prevent the starter from engaging.
3. Check the wiring. The wiring between the battery, starter, starter relay, and ignition switch can become loose or damaged, which can prevent the starter from engaging.
4. Check the flywheel. The flywheel is the large gear that the starter engages with to start the engine. If the flywheel is damaged, it can prevent the starter from engaging.