Trying to add an effect

I’ve been researching about adding effects on the layers, but all my tries didn’t work. This print is the last so far. What happens is that I follow the instructions at the manual, but when I change the effect values, nothing happens to the drawing. What’s wrong?

Manual:
http://docs.toonboom.com/help/animate-pro/#HAR/Stage/019_Effects/055_H2_Contrast_.html%3FTocPath%3DToon%20Boom%20Animate%20Pro%20User%20Guide|Toon%20Boom%20Animate%20Pro%203%20User%20Guide|Chapter%2018%3A%20Effects|Using%20Effects|_____18

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Thanks!