Background from Transform TOP not visible in kantanMapper

Hi all - kinda newbie question . . .
I am adding a white background color to an image via a Transform TOP with ‘Comp over background color’ = ON. But when I pipe this into kantanMapper I’m not seeing the white background in display. How would I accomplish this? Maybe a setting in kantan I’m missing? Or some other way of adding a basic white background to the image?
Thanks
Background Color via Transform TOP.toe (290 KB)