Thanks guys for the replies,
I'm going into the color page from the main timeline and selecting the compound clip from there. But think I understand now what's happening. I have key-framed the power window mask to move upward so that it follows the tape ejecting from the VCR in the video clip (screengrabs below). And while the mask is animating fine it is not bringing the compound clip (that it is applied to) with it. Im trying to do in resolve what I would normally do in Premiere Pro without realizing that power windows work differently. My bad. Unless of course there is a way to move the compound clip with the power window?
Basically I am trying to create a white VHS tape label with text that appears to be on the tape as it ejects from the VCR but I have yet to grasp how to do this in Resolve. The first screengrab shows the tape fully ejected and the second one shows it partially ejected. As you can see in the second one the mask moves but the compound clip remains stationary.

