To allow mapping of flat bar from advance steel to revit, revit needs a flat bar family.
This family needs to be included in structural framing folder in revit.
Mapping rules need to established.
Without this elements like flat cross bracing, bottom flange spreader plates are not transferred.
Similarly tapered beams can use standard flats as well as plate sections, so to allow transfer and sync , this kind of table/family needs to be in place.