controlling Volta playback

I have a first ending that spans 4 measures. When I put the volta in it initially spans just the first measure. I grab the right-end handle and stretch it to span the 4 measures, but the playback only skips the first measure.

It's as if it thinks the volta only spans the first measure. I see magenta anchors that suggest the volta is only spanning one measure, but can't figure out how to move the right anchor.