Can't properly rig this model! Help!

Here’s one of the models I rigged using Custom NPC Maker plugin. Everything is rigged properly and the NPC walks smoothly and naturally.

But for some reason, I can’t get this model to rig properly.
image
The green lines are always lower than the model’s arms and for some reason I can’t move it up to properly rig it like I did with the other model.

https://i.gyazo.com/8f1384b1e0d4ff9565136c778fbe13ed.mp4

As you can see from this video, the green line between the arm and the torso won’t move to the right spot. Any idea how to fix this? Thanks
helpmeplease.rbxl (704.6 KB)
Here’s the model if you guys want to experiment with it. Thanks