by premitting that I have no basis on surface modeling, following a tutorial on youtube I managed to create one:I have the problem of having to convert it to solid and this error appears to me.How can I solve it?
to build the solid the surface must be closed (such as the surface of a sphere), or it can be opened as long as the opening is filled with a flat face (e.g. a cone with the open bottom, or a cylinder with base and open tops), in those cases, the system recognizes that for the closure it lacks "only" the flat surface and generates it automatically.
in the case of the door, or of the window, the only surface is not enough, it must be completed with other surfaces (the edges and then the inner surface), so they go together and only then you can close it in solid.
Depending on the shape you need, you can use the surface command with thickness that generates a solid with edge at 90 degrees compared to the surface, or the prism command that generates the solid but from the ability to define the edge direction.
