I had a similar problem with a Yanmar YM276D, which in it's day I think was very similar to a JD850 or 950. My Yanmar had a clutch and a "Shuttle" shift, and you had to fully depress the clutch to activate the safety switch, under the clutch pedal in order to start it. I didn't get any clicking noise in the crank position just a complete nothing. I did however still have the dash lights, and all the headlights and flasher lights worked fine, which to me indicated the battery wasn't the issue but she just wouldn't start.
I struggled with the thing, thinking it was somehow a bad/low battery, because it would always start if I used a jump from another battery. Finally, I had my guys at the shop rewire it and bypass that safety switch and voila.......end of the problem. She started every time after that. Somehow, the battery couldn't push the voltage through that switch, without 2nd battery boost along with it.
REV