When I run your model on a Full License, here is the summary.
--- Number of total nodes = 28239
--- Number of contact elements = 81988
--- Number of spring elements = 0
--- Number of bearing elements = 0
--- Number of solid elements = 25403
--- Number of condensed parts = 0
--- Number of total elements = 107391
The contact elements are causing your model to exceed the 32,000 element limit. They aren't created in Mechanical so you can't see them till the solver runs, then they are created, pushing your model over the limit.
If you delete all these bonded contacts, the solver will start.
However, the solver will fail because you need to add some beams to connect the studs to the OBS and to the rails.
You still have a row of nails on the top and bottom that you don't need. The bottom nails because the bottom rail is gone. The top nails because the top rail is sharing topology with the OBS as shown by the purple line at the intersection.
I reduced the mesh density and put back one bonded contact of top rail to studs and this will run. Archive 19.1 attached.