I was leveling some ground, raising and lowering the blade as I drove. The blade stopped responding. I checked the fluid level, and it was rusty orange...so I drained both the rear and center reservoir and re filled them. It made no difference. I moved the lever to disengage the PTO then re engaged it. That made no difference. The engine and transmission seem fine... Any suggestions?

Thanks to people much more knowledgeable than me, I was guided to open the inspection panel on the side of the PTO housing. The spring was assumed to be the problem...and that was sort of correct, but the spring itself was actually OK, but the mechanism it was connected to was not moving freely. I moved it around until it did move freely, then replaced the inspection panel. It is now working.