Draw Mask Keyframing to make the mask move

what am I doing wrong?

Drawing mask animation is not adjusted with "Transform: Position". Please adjust using Video Inspector: Drawing Mask: Control Points: Keyframes.

First thought that comes to mind is: did you try the magnetic mask? Maybe it does not work due to the similar colors, but if you didn't, try it. You may be surprised.

If you do proceed with the Draw Mask: there are two sections where you can use keyframes, namely the Transforms, which affect the mask as whole via scale, position and rotation, and the Control Points, which affect the individual control points of the mask. You can use both, as needed.

Adjust the mask as you want it in a given frame; then set a first keyframe, by clicking the diamond; then move the playhead to another frame where you want the values to change, and any changes (should) result in a new keyframe.

So, for example, move to frame 1, add the draw mask, adjust it; add keyframes for position and for control points; then move to frame 2 (if you need to do it frame by frame) or frame 10, say; any adjustments you make will result in a keyframe there; and so on.

LocaAlicia: to be clear, I meant the "Transforms" within the Draw Mask effect itself (as seen in the image below). This moves the mask as a whole, and can be combined with changes to the control points themselves.

You haven't responded to any of the suggestions yet but my first thought was the same as Luis' . . . have you tried the Magnetic Mask as it would keep everything quick and simple . . . assuming it will work with the closely matched colours?

It sounds like you're on the right track with keyframing the draw mask's Position property. Make sure to adjust the points of your drawn mask frame by frame as needed to follow the outline of the moving subject. Keep practicing and you'll get the hang of it!

Thank you for the addition Luis👍

Have you tried any of the blend modes?