I have been having an issue where I want to include a separate object (eye) and weight paint it to the same bone as the head. When I select the armature, and the eye object, then switch to weight paint, it will not allow me to ctrl click any bone. I am only able to have the entire armature selected and then paint the eye. Every other object on this model does not do this. What is missing from the eye that that the other objects have; why can I not select any bones to weight paint this object?