The first thing to check is to make sure the parking brake is not in the locked position. Next, check the linkages for breaks or damage; if they are broken or damaged they would need to be replaced.
If that all checks out ok then inspect the hydraulic pump belt for wear or damage, if there is wear or damage replace the belt. Inspect the hydraulic system to see if there is fluid in it.
Check to see if the bypass valve is closed, if itâ€™s in the open position it lets the mower be pushed manually when the engine is off, but it should always be in the closed position.
The model and serial numbers on your Snapper zero-turn mower can be found on the frame of the mower.
NOTE: if you need a part for the small engine in your Snapper zero-turn mower, there will be a separate model/serial number for the engine. Here are the small engines that are available in your Snapper mower. Visit the page of the engine you have to find out where the model/serial number is located for your small engine model: