I have the issue solved, though I don't know the "why", just the "how". I moved the subassembly out of the assembly it was in, and then moved it back in. Now the round bar is selectable. The job can be done now, but it does not make any sense to me.
That being said, I am using the IronCAD Drawing space, and the version is 2020, which has been updated to the most recent version. When I deleted the view and recreated the it, the issue had persisted. Not sure if this info matters, but if it needs to be collected, there it is.