It appears to be working now. The only thing I did differently is to have gables enabled before copying the file from MFCG into City Viewer. Thanks!
Is it possible to add gables to a city imported from MFCG? I'm having trouble with this file... https://drive.google.com/open?id=1mGmdUilOODNJA6X86qWowZQip9Te33hH