I have a problem that the physbones setup doesent work in play mode for some reason. (1st pic is normal mode and 2nd is play mode) The only thing I done before the physbones broke is i separated some clothing in blender, exported it to the same fbx the prefab uses and then the physbones stopped working. Maybe theres a limit on the amount of physbones?
Your physbone is disabled in the second picture, perhaps by an animation.
Found the problem, it was FX layer for some reason