It could be simply were the gears are sitting . Sometimes mine will shift just fine other times not. Sometimes just bump the starter will help. I've found that with the tractor Off you can turn either the rear or mid PTO shaft by hand just a bit and it will line up the gears and allow you to move the lever easliy.
I was putting my BX2200 mower deck back on a couple days ago, after performing routine maintenance, and the mid PTO and the rear PTO would not turn by hand, with the engine off of course. Helpful if the mid PTO does turn, when hooking the driveshaft back up.
So I moved the PTO selector. At one point I found a position where the mid PTO was free and could be turned by hand. Got the mower driveshaft hooked back up, but then I could not get the PTO selector to move back to the mid PTO position.
This has happened to me before, and since I only use the mid PTO on the BX, I actually wired it so I can not accidentally bump it out of the mid PTO position.
To make a long story short, what I did was engage the PTO briefly, and disengage it, while the engine was running, and after a few tries something shifted and I was able to get the lever back to the mid PTO position, where I normally keep it.
Perhaps the OP might try this as well.
I do not think forcing things is a good idea, as something could end up being bent internally, which would not be good.
I never thought about trying to move the unlocked PTO shafts (with the engine not running) which could be a great solution. Would have been difficult for me with the mower hooked up, but maybe I could have moved the rear shaft, don't know...
