Arm IK doesn't work

Sorry, don’t have computer with me to try, and i assume you have read Adobe Character Animator Help | Control puppets using behaviors (the section on arm ik, with video)

If you put a dragger on the hand, does the arm sort of move like you want?

The examples i have seen in the forums create an independent layer for the arm then attach to the shoulder. A mistake in that case is the shoulder tag must be on the body, not the arm. You might like to exprriment creating a Left Arm layer, put all the arm parts in it, make it independent, put the shoulder tag on the body where the arm attaches, the elbow and wrist on the arm layer. The docs does not say the arm needs to be independent, but the examples i have seen do that.

The IKArm behavior relies on various tags like wrist and shoulder, I could not see them in the screenshot,  Can you share a screenshot showing where the different handles etc are?