I have an older Ariens single stage model ss522. I can't get it started. Has fuel and spark.

Hi,
You have a 938xxx family of snowthrower. It has many varieties however, including both four cycle and two cycle engines. My first guess would be that it is the carb though you say you have gas. Also, be aware that most of those machines have solid state ignitions which means they will still have fire with a sheared flywheel key; it just arrives at the wrong time.
Peace,
Clarke