Sorry, I should have posted some instructions for the script. 

The "no match" results should indicate that there are vertices which aren't symmetrical, in your base mesh.  The listing only comes up when vertices which aren't centered on X fail to find a matching vertex on the other side.  Or if the central line of vertices isn't zeroed on X, possibly.

All functions in this script use a simple lookup table to match vertices, and don't hunt through the mesh looking for a best match, if there isn't a match found at coordinate -X,Y,Z.  The script which requires the Spanki extension can handle that, however, correcting small deviations or asymmetries.

Mirror copies one side to another on an actor with a base geometry which is centered on X.  It creates a symmetrized morph which includes the source morph.  It sounds like your results could have been generated if the script failed to find any matched vertices on the left side of the mesh, so you just ended up with the source morph with no mirrored deltas mixed in.  (Mirror will also produce odd results if, for instance, you use "+x to -x" and then select a morph which is on the right side of the actor (or vice versa for left).)

The Flip function would actually be the function you'd want to use.  It will completely flip the morph on X, producing a morph with both sides of the original reversed.  Flip also flips a morph between right actors and left actors, such as with the thighs.

I guess the terminology is a bit confused in my usage.    I was thinking of the Mirror Morph utility, which only copies one side of the morph to the other side, when I chose to use "mirror" as I have.  Maybe I should call it "symmetrize".

I may be completely wrong about asymmetries in your mesh.  That's just my first guess, based on the information you've given me.  My apologies if this seems like criticism of the model.    Such is not my intent.  My tests after reading your post could only produce odd results if I used settings which mixed up the +x and -x, as described above.  I could be completely missing something.

Anyway, you'd want to select: Flip  -->  actor  --> morph.

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.