Add Surfaces to Named Selection

A_Proger

I have a rack that was brought into Mecway as a step file. I used Gmsh to create the mesh, using the below code to combine the geometry. I added boxes to the shelves to run a analysis on the assembly, each has their own mesh and density to align with their weights, when attempting to bond the box to the shelf I added surfaces to a named selection to each self and applied the bonded connection but get an error "This load or constraint is not applied to any faces. Is this possible? Do I need to bring in and create the assembly in Mecway for this to work? When I click on the master surface which is the shelf it doesn't highlight the surface like the slave on the independent box does.

SetFactory("OpenCASCADE");
a() = ShapeFromFile("C:\Full\Path\To\bracket_assy.STEP");
r() = BooleanFragments{ Volume{a()}; Delete; }{};
Physical Volume("Combined volume") = {r()};
Physical Surface("Combined boundary") = CombinedBoundary{ Volume{r()}; };

Thanks in advance for any advice.

Tony