Awning cleaning need help with proper cleaning agent

I have an awning cleaning job that we began today and told the customer we have to come back. The reason we stopped is the spots on the awnings, they are green lichens, basically its a yellowish green moss on her blue awnings. I need to know of a cleaning product that will remove the junk and not ruin the canvas. What product could anyone suggest? Prefer something that will seal it as well

Deep clean by Titan, or LA Awesome. You could add a small amount of bleach if it does not work. If the awning is vynl you will need to seal it with Windsol.

John Lee Window Cleaning
Maryville TN
865 310 0728