Why did my engine not starting when the dash board light is on

I would 1st check to see if you have at least 12.5 volts at the battery + give the terminals a little tug to see if they are tight. If all is ok at the battery, test the fat wire at the starter - should have battery voltage all the time. the small wire at the starter should have voltage when the engine is cranked. If voltage at the starter looks ok, suspect the starter, otherwise trace the problem in the starter circuit