Mmm. What happens if you try one (or more) of the other drivers? E.g:
/vis/open TSG
or, to be really sure this is only a graphics problem,
/vis/open TSG_OFFSCREEN
and at end of run
/vis/viewer/refresh
This should create a file something like g4tsg_offscreen_zb_png_1.png which should show the detector and, if you have /run/beamOn with trajectories activated (/vis/scene/add/trajectories), should show trajectories as well.
There have been issues when building both Qt and X11 on some systems. Try rebuilding without X11.