Hybrid CADfile w/ *.GP4 Xref

Just opened some hybrid dwgs w/ *.gp4 Xrefs, which I created in AutoCAD a couple yrs. ago.
Cannot view the *.gp4, only see the path/filename for the Xref.
It sure jogs my memory that I asked that question last summer before we purchased BircsCAD & I remember getting an affirmative answer that BricsCAD DOES indeed support the *.gp4 file format.
So, what do I need to do to get BricsCAD to display the *.gp4 Xrefs?