Quit running suddenly, won't start. New plug, new gas, filters clean, fuse good, safety switches working. Engine turns over, will not fire.

Most likely a failed safety switch but lets start by checking for spark. Pull the plug wire, remove the plug, reattach the plug wire, ground the plug to the engine block and turn your key. As the engine turns over (quite freely due to no compression) do you see a spark on the plug tip?