Adobe Premier Elements 3

I have a video program that has most of the program in stereo. One clip is mono. I can see audio in the left channel and nothing in the right channel.

I am trying to apply the audio Effect Fill Left to create a right channel and it is not working.

I separated the video and audio and dragged the Effect - Fill Left to the mono audio to create a right channel... nothing happens.

What is the trick to applying this effect.

Cheers! PHIL