Hidden step for bindings in a swap set??

I've been bashing my head against this for a couple days now.  Help?

I'm using a swap set so my puppet can have different eyes for different emotions.  His neutral face works just fine (sorta - when live, his blink eyes sometimes have weird masked shapes and I have no idea why.  But then if I make some tweaks elsewhere in the project, then they'll be fine.  Until I make tweaks again.)

The problem I'm struggling with is his angry eyes.  They're just 2 basic AI shapes that I want to bind to my eyebrows, but they just won't budge.  I think I've set them up identically to the neutral eyebrows but no movement at all.  If I bind them to my upper eyelids, then they'll wiggle a bit, but that won't do because my eyelids aren't as expressive as my eyebrows.  

What can I possibly be missing?

Thanks so much!