Panning lost on tracks when plugin (send) is activated

I have two vocal tracks, one panned completely left and the other panned completely right. The panning works fine until I activate the Abbey Road Chambers plugin, then both vocal tracks sound like they’re coming straight down the middle. I’m using the mono/stereo version of the plugin as a send for both vocal tracks in the post-fader position. Can anyone explain what I’m doing wrong?

I’m using Cubase 12 Elements. Any help would be greatly appreciated. Thanks,