I'm working on this scene with the Storybook Carousel:

It rendered fine (obviously). I saved it, and reloaded it fine. But now after I closed and reopened Poser again, the Carousel no longer shows up either in the preview or in the render. Changing the display mode for the carousel does not make any difference. Changing the skinning mode does not make any difference (but I'm currently set to unimesh, and no subdivision). It still appears in the hierarchy editor, which indicates it should be visible. If I pick the carousel or any of its parts, the properties also show that it should be visible. Almost all the other figures are parented to it, and if I spin the carousel, they all move as expected. So it seems to be here, just... not.

I also went through and double-checked all the materials for the carousel. I previously converted them all to PhysicalSurface with Ken's script, but just to be sure I went through and deleted all the PoserSurface nodes, removed everything irrelevant, and made sure PhysicalSurface is the selected node for FF and SF. So there don't appear to be any issues with the shader nodes. No change though.

Any suggestions before I send this off to support?

(Also, if anyone knows why all my Hivewire Horses ran away...  ;)   )

Was there any figure attached to the carousel that was turned invisible?  The Hierarchy panel should also show if it is visible or not (the eye next to the content).  The visibility eye should not be grayed out.  Everything you described should not present a problem.  If it was material shader related, you would still see the object.  It almost sounds like a file corruption.  At this point, I would restart the whole system and open the Poser scene again.  Otherwise, submit a support ticket.

None of the eyes are greyed out.

I didn't hide any whole figure. I mean, I hid the girl's toes to prevent pokethrough, but that shouldn't do it. I'll try a restart.

Hopefully, it wasn't relocated somewhere else in the scene.  Try using the Pose camera with the carousel selected.  That camera will immediately point in that direction.

I'd also double-check what geometry file loaded. I've had things that loaded correctly the first time but when I reload the scene it loads a different file with the same name. There's a script under print info called list files that will give you a list of every obj and texture in the scene including the complete path so you can see if it's sharing a name with something else.

Good thoughts. The pose camera centers in the middle of everything. There is a red selection circle around the middle of the scene (which should be the middle of the carousel), but it's too small. If I increase the scale, all the parented stuff gets bigger and moves up, and the red circle grows, but nothing new appears.

The list files script tells me "Runtime\Geometries\Anniemation\Carousel\Carousel Complete.obj" got loaded, which looks correct. There is also a "Carousel Complete2.obj" in the same geometries folder, but Carousel Complete.obj is the one referenced in the .cr2 file.

What other diagnostics have we got hiding in there? I ran printGeomStats and it says this, which seems problematic:

Carousel 2
     Body     no geometry
     CenterOfMass      360 polys          324 verts
     GoalCenterOfMass      360 polys          324 verts
     base     no geometry
     poles     no geometry
     auras     no geometry
     emitters     no geometry
     lights     no geometry
Carousel 2 totals --> 720 polys      648 verts

I'm sure there is supposed to be some geometry for those parts. But that seems to indicate the problem is loading the geometry rather than some kind of display, position, or scaling issue.

Ok, spoke to support. It looks like RedPhantom's idea was spot on. Support noted there were no facet groups in the .obj file (which would be lines starting with "g") that I sent them. And Poser needs those to assign the geometry to the figure's body parts in the scene.

However when I did some additional looking around (thought I would compare the .cr2 file to see if it had any hints), I found there was another copy of the .obj file by the same name in the Characters folder. So I guess initially it pulled the one from Characters because it was in the same folder as the .cr2 file, but on reloading it went for the one in the Geometries folder, and that's what failed. I copied the one from Characters over the one in the Geometries folder and it worked correctly.

RedPhantom's evaluation was accurate, and I concur. The idea had occurred to me as well. Poser often links to the wrong file when files with identical names in its Runtime or spread across various runtime directories.