Answer:
First check the 12 volt battery for 12 volts. If you don't have a volt meter then turn on the lights and see if they are bright. If not check connections. Then recheck. If the battery and connections are good then you will need to check the starting solenoid if equipped. Then finally pull and check the starter. The connector can look good but have enough corrosion as to prevent starting. Pull the connectors and clean with a wire brush. If you pick up a tool a the local auto store its only a couple of bucks and cleans the inside great. Then reinstall and tighten the cleaned pieces.