I have checked the netural switch and the break. But cannot drive it is a hydrostatic mower and the model no is 40901x5a . It worked just fine and now it will not drive . Is there a safety switch or something that I am missing . Please help

Hi,
I gather it runs, so it is liable to be the drive belt, an idler or a tension (extension) spring. Could be a combination, an idler that takes out the belt.
Peace,
Clarke