Not seeing drawing substitutions

Hi, I’m new to Toon Boom and am trying to import a character from a PSD and get the different mouth shapes to work with drawing substitutions. I imported the PSD as individual layers and copy/pasted a couple of mouth shapes onto different exposures on the same layer, but I’m not seeing them show up in the drawing substitutions slider. All I see is the full character. Is there something I’m missing? Thanks!

How specifically were the PSDs imported?
The drawings for the mouth shapes must all be in the same mouth layer to be able to substitute them.

In the Xsheet window are the Drawings labelled A to F if you’re doing lip synch detection?