If you have tried almost everything to get the mold
out, then other than painting the surface the only way to completly remove it is to re cover it. As the vinyl breaks down with sun exposure it alows water
to pass through. When that happens the mold is inside the fabric
and probably inside the foam underneath. Sometimes using bleach and other heavy duty cleaners will make the vinyl look good temporarly but you will see the mold return very quickly there after. Sometime the cleaners can actually cause quicker breakdown of the fabric
and cause the vinyl to breakdown quicker.