Does CPU rendering work in P13? If so, that clarifies the issue is GPU-related and not a more general problem with the scene.

All gray seems suspicious. If you look in the upper right, is there an icon there with a dialog bubble? Click it to see the log. Is there a CUDA error? If you do have one, you'll need to close Poser and re-open it. Sometimes the skinning mode seems to be an issue here: select each figure, go on the menu to Figure, change it to Unimesh. Could also be an issue with a particular shader, the log might give a hint about which one.