first, to pattern the surface, you will need to pattern it as a body, not a feature.
second, there are a couple of ways to solidify a surface.
a) if the last feature that closes your surface is a merge or fill, there is a checkbox in the feature property manager for making it a solid.
The pattern "Bodies" was the key.
I did not think of that or know that would work.
I do a lot of multi-body parts which include patterns and it is frustrating that it always defaults to “Features to Pattern”. Oh well, what’s another mouse click?