Opacity mask created in Premiere not working In After Effects project

I’m relatively new to After Effects, and am having trouble with a mask that I created in Premiere to remove an object, but the mask doesn’t work in After Effects.

I'm doing a project where we shot a bunch of monologues in front of a green screen. I did the basic edit in Premiere, but then took each monologue into After Effects to Key it, and then do some VFX blending of the person and the plate, using Red Giant plug-ins. I’m using the most recent version of Premiere and After Effects.

For one of the actresses, we used a pony clip to gather her jacket in the back. It's not in the shot, no problem. Except, of course, for the two times she pivots, gestures, and then we see the pony clip, right at the bottom of the screen. Completely missed it while filming. It's by far the best take in each instance. Ugh.

The pony clip is only visible for 10-15 seconds total, so it's not like I'm taking it out of every frame for 100 seconds.

So while in Premiere, I create a tracking mask, going frame-by-frame adjusting the mask size and movement. I take the mask's opacity down so that it goes transparent. No problem, because all of this is over a plate. And it works. Yay me, I'm brilliant....Until I send it over to After Effects.

The mask is still there, but it's not cutting out the pony clip. It's moving in it's track, but I still see the clip. I set the mask to subtract, still there. I set the mask to add but hit the invert box, still there. Now when I set the viewer to only see the mask, the mask is there and it's working. No pony clip. But when I go back out into the composite view with all the layers and effects, boom, the pony clip is still there. I then go back into Premiere, and the mask is still visible.

I'm sure that there's a simple toggle switch or some darn thing that I click and the mask will work, but I sure can't figure out what it is.

I tried to use Content Aware Fill but got the all target frames are completely opaque error message.  Do I need to use that before I chroma key the footage?  Would that work? 

My worst case scenario is just blow up the performer's layer and reframe it so that the clip is out of frame (shot in 4.6k, editing in 1920x1080). But I want to figure out how to take it out.  Also, my apologies in advance if the answer is obvious or has been covered elsewhere.