Problem with connecting armature to a part of the body

Greetings, i am fairly new to to blender and i’ve been using it for a few months so i know many of the basics. Recently i tried making a rigged character but i’ve ran into the problem.

So baiscally my character is made out of multiple parts and all parts of each limb is joined together as whole and then joined all the body parts together, i created a rig for the body following a tutorial yet i remained puzzled by this issue. Every part works well and moves perfectly for example the legs, yet when i try to move the arms of the character parts of them seem to stay in place.

I guess its a parenting issue have you checked it? Or set it up again following the tutorial there might be somewhere a mistake. But Its hard to tell. Your elbow pivot is also not following? Is the geometry parented to the Bone?

From the picture i cant see much whats going on.