Can anyone help?

Is this a tractor? What do you need to normally do to get the blades rotating?

Yes this is a tractor... After you start the mower there is an engage stick that you push up and hook to the right to hold it.

With the engine NOT running get down and watch the movement of that stick and how it affects the belt to the blades pulley or the pulley running from balde tot blade. All those belts should get very tight when you engage the blade. If not you have a broken belt, stretched belt or a spring has fallen of the spring tensioner pulley.