2D Animation Package: Am I doing something wrong, or is Auto Weights not working?

My character has this arm joint that doesn't move the way I'd like:

I'd like the shoulder/collar of the body to deform with the arm movement. Right now, it's completely detached and moves like a paper doll with a push-pin through it at the start of the green bone.

I thought the issue with this would be about bone influences and weights, but the body has these influences:



And the arm has influence on the chest:



I notice that the body has no "green" weight in it and the arm has no "yellow" weight in it. I think this is causing the "paper doll" effect. But when I press Auto Weights -> Generate, it doesn't change anything. Here's after I press it:



Shouldn't generating weights -- now that the arm bone is included as a influence -- cause some green to go into the body or at least change some of this color?

Am I doing something wrong, or is the button not working correctly?

My bone hierarchy may be helpful, so I'll include that, too:

 

Thanks for the help. How do you do this one? Do I double click the body sprite and then create new edges/vertices?