OP has mentioned that this is a 2012 Troybilt model 13WN77KS011 Appears engine model number should be a 31C707-3346-G6. May need to confirm with the numbers on the valve cover.
Does the engine appear to turn slightly and then stop, or starts to turn over like normal and then suddenly stops. If so then follow what I posted below.
Remove the valve cover and with the spark plug out turn the engine over until both valves are closed and the piston about 1/4 inch below TDC. Can be confirmed by either a light into the spark plug hole, or by putting a pencil in the spark plug hole to confirm position. Then check that the bottom valve clearance is .004-.006 and the top valve clearance is .005-.007. After you have confirmed both are within spec then roll the engine by hand and watch the valves, most likely the bottom valve should bump off of seat slightly before TDC on one of the strokes. If no bump off, that would mean that the compression release on the camshaft has broken.
Seems strange that it could happen like that but I guess the sudden stop could of jammed the mechanism.