Is it giving an error code? There should be a label on the inside of the door telling you what the codes mean.
Also, if by "not working" you mean the coin drops through or jams, make sure you have the proper coin in the coin comparator.
Also, sometimes they get weird. Sometimes you have to open the door, then turn the jackpot reset key, then cycle all the way through the tests, then wait for it to spin around again, then add a credit via the button on the coin comparator board, then pull the handle and watch it spin and stop, then shut the door (with the latch all the way down) then wait for it to spin and stop, then it will work.
If you have an error code, then we can see what is needed to fix it. The biggest problem is the 61 error - meaning a dead battery. If you can solder, you can replace it, but then you'll need a Clear chip (and a Set chip if you have a dollar bill validator) to reset the CMOS before it will play...