Is this the two-cycle of 4-cycle? Which model? How old is it?
Have you checked for spark? When was the last time the valves were adjusted?
You can check for spark by removing the spark plug from the engine, putting the coil wire back on it and placing the plug in contact with the metal block. In a shaded or darkened area you should see a nice blue spark. Be careful and do not to touch the plug or wire while doing this, so you don't get an unpleasant shock.
Let me know and we'll continue.
Then you probably have a bad ignition module, but let's make absolute sure by:
If you do this and still do not have spark, the coil will need to be replaced.