mask turns screen black

Hello After effects community. When i use the pen tool to draw a mask around something i want to track, the whole screen turns black except for the inside of the mask. It has never done this before until today. Can somebody please help me understand why it is doing this all of a sudden. for instance i used to be able to use the pen tool to draw a mask around the eye of my subject without the screen turning black, but now everytime i trace something the screen goes black. I am attacking a photo of what i am used to it doing vs what it is doing now. please help.