The above picture shows the mask I have created in layer 2. The mask is set to Subtract blend mode I then add the portrait png file under these as a 3rd layer. Normally this would only show in the composition within the mask created on layer 2.
I have changed the different settings on each layer between add, subtract, normal and none and also the mask blending type as well. The composition always shows the full image rather than it being the bottom layer. I know this is very basic and the same process seemed to work on a previous project only last night, so I'm sure it's not my computer or a bug. I have tried adding the same video clip again as a third layer and yet the mask on layer 2 still doesn't affect it. I am trying to get the picture in the bottom image to fit the mask in the top image basically.
Remove the effect on that Layer 2. See what happens.