Object Mask Effect not working in Sequencer UE 5.1

Hi, I am following this tutorial to mask out object in UE 5.1 I managed to make it work BUT once I add the cube to sequencer and start adding key frames , it does not work anymore. meaning the mask/stencil is left behind in the first key frame and no longer updates in the viewport. any thoughts how will I make this work in the sequencer or are there any other way to do this method that works in the sequencer?