I have began to have this same issue on Windows.
V4 and M4 have always been in the same runtime for many many years. It seemed to be after my last install of P12.
I too re-downloaded all my V4/M4 files from DAZ and reinstalled them (same external runtime) and still I can not get the FBMs to appear but can access on individual body parts.
LeFemme and L'Homme are not effected and some of my old V4/M4 characters still show the FBM but only when I try to build a new character......???