If it has 2 grease zerks, there is a roll pin through the hole in the shaft under them.
Remove zerks, flush out grease, and you will see.
Often pin is worn, or broke, and hard to get out. Can be more jammed on with bits of broken roll pin.....
If ORC spins both ways, likely the dogs, or teeth, are worn off or busted. They would not be holding the ORC onto the tractor shaft tho.