Ryobi circular saw motor runs, blade doesn’t
Replacementparts.com show s no gearbox for this saw so it appears you have a snapped shaft. The armature goes for about $59 and you could get a new saw for that amount so it's not worth fixing. Numerous other parts are no longer available so don't waste your money. Just for fun, take it apart and see what happened. If you're in the USA, you have time on your hands.