Sorry for the lack of a better title, but since I don't know what the problem could be...

I've cloned the comfy pet pillow to add a cardboad box around it, like a cat would sleep in a box. Did mesh and UV in Blender, and modified (actually just resized) a free texture in GIMP. Followed a few tutorials as to how to link the material and texture to that newly added mesh. Mesh is not joined to the existing cushion, they are two groups (named cushion -- original -- and box -- the one I added). Both texture and mat are cloned in SimPE from one already present in the package.

The mesh shows up just fine in game, but texture won't show up (flashing blue). I reviewed my changes and actually tried building this package more than once.

The only part I wasn't sure of was that the original texture I've cloned had a clean/dirty state, so I removed the clean/dirty part in the name. I don't know if there might be something else that needs to be changed about it that is confusing the game (I'm not sure how the game handles the state, if it's just a swap of texture depending on the state or if it's more than that).

I've attached the package in case someone could figure what's wrong so I can finally learn something.

Take a look at your package in the Scenegrapher tool in SimPE ! You will see that from the SHPE-item (cardboard_pet-bed-root-rot) there is a link to a TXMT with no TXTR-link. This TXMT has wrong name in the SHPE, in the Parts tab (missing a "_box_" in the name)!

...and - with a multi state object, you'll want to check the Material/Material Names in the STR to make sure none of the lines are missing the ##0x1C050000! prefix. If the object has on/off BHAVs, you might have to check that they're linked to the STR too, doing a fix integrity can break the links. (Your pet bed doesn't have on/off BHAVs so no worries there.)

Ah! The tutorial I was following wasn't clear enough (or said better, I didn't read it well enough). I though the name of the texture was required there, but it's in fact the name of the file of the texture. Got it now. Though I'm still unclear as to the role of the SHPE thing.

Now that I fixed that, there is another problem. Now my cardboard texture (which works perfectly fine on the box) somehow gets blended in with the texture of the cushion on the cushion. Basically, the cushion flashes between it's original texture and mine (which shouldn't apply to it at all). Suspecting a wrong setting in the material definition, I compared it to some other random object (a table I happened to have extracted), but I don't see a difference which seems significant.

Can you, or someone else, help me learn something more?

The box in your mesh, the GMDC contains the same cushion as the cushion. You need to remove it from the box.

Oh! Not sure how this happened, but happy to find it's an easy fix! Thanks!

Since this test is working, I guess I can move on to my bigger "real" projects now