Easiest method for roof stain removal?

Im selling this house and cant seem to get rid of the roof stains with only powerwashing..

Is there an easier way to get rid of this stain?

I am in Upstate NY

They make products you can just spray on the stain and let the rain wash it off.

Did you spray some clorox bleach or anything on the spot and let it soak in before you power washed?