Cannot select the rig

Hello. Right now I’m trying to make a viewmodel for a first-person gun system. I am however having issue - I cannot select the “human” part of it (head, torso and arms), what makes it impossible to use the plugin that I’m currently using to rig it. The parts act like if they were locked but they aren’t. How do I solve this issue? (This is not the plugin’s fault because the normal select tool doesn’t work as well.).

EDIT: The selection only doesn’t work on the head, torso and arms. It works on the other parts.

EDIT: I fixed this by setting their CollisionGroupId back to 0. Somehow the collision group was making me unable to select it. How do I fix this?.