Help circle effect

Hi all, I’m new here and to Flash as well C:-)
I’m trying to make a mask effect where circles would appear randomly on the stage showing the underlying picture.

The circles are instances of a movie clip that’s simply a small circle getting bigger…problem is only one circle appears, eventhough i have a for loop to produce 15 instances (tried with a while and same result)

could you take a look at my fla and tell me what I’m doing wrong ?