Can't help out with a diagram - possibly flat battery, battery connections, PTO switch, motion control lever switches, park brake switch, seat switch (if required for start) and adjustment of each of the switches. My red zero turn had a heap of leaves/grass built up stopping one of my motion control levers from fully sitting in place an inhibiting the start, don't know about yours, but perhaps worth a check. I seem to recall someone else here having trouble with a park brake switch recently on a similar model but don't recall the outcome. If it cranks, follow 85Hokie's post.