I should have stated that I have cushions and not an umbrella. I will try washing my umbrella though!
Site states it is for hard surfaces. I need a product for fabric use.
Have you tried Iron Out? https://amzn.to/2EjV9Vn
I have tried it but with a small amount which did not work well. Nervous to use a stronger dose for fear of ruining the fabric. It is a rusty orange in color.
Check out this article.