Masking of a duplicated MC

dear flashers,

I search my problem in this forum prior to writing this. I got a thread that explains exactly what I needed to know; however, it doesn’t work for me…

I am trying to mask a duplicated mc.

I am attaching my .fla so you can take a look.
The code is a bit long, but I marked the setMask code line with dashes (it’s right on top).
I marked out the setMask line so you can see how it looks like, because when I do mask, you can see any of the MCs that are being masked.

Thank you,