Why it wasn't working, and neither was your good advice...

So, I finally got it to work, but here was the main issue: my footage was short, about 3 seconds. But I wanted it to loop for 20 seconds.

However, once footage on the layer runs out, it stops looping, and then runs blank for 17 seconds.

To get around that, I had to precompose the initial 3 seconds in a comp that was 20 seconds long. Nesting that precomp into a 20 second composition allowed the looping to go the whole way.

So, until I figured that out, nothing you were telling me was going to work. But it wasn't wasted -- now it works.

Thanks for the perseverance.

Mike