What am I doing wrong, where it states "RH" in the RH Alleyway compositor group, there is a wall which should cut off the white circular highlight, for testing purposes I have cut off the circular highlight even more in the image editor with the mask drawn, yet in the compositor nothing is happening. I want to use the mask to subtract from the image (or alpha channel) so it cuts off. This mask will need to be animated or assigned to a track marker to keep the wall occluded by the one in front of it.

Edit 1: I have also tried a set alpha node and plugging the mask into that and it also doesn't have any effect on the layer.