Instanced Static Mesh not working with a specific mesh -- why?!

I’m using Instanced Static Mesh Components in my game, and I’ve had this working fine for months. I recently updated ONE of the models I use and now it simply shows up with no material (default grey-grid material).

I can put the MATERIAL from that new model on one of the old models and it works (old model with new material shows up, ie, the flag for instanced rendering on the new material is set correctly).

I can put the entire model and its material into a regular static mesh and it works fine. The problem is only with instanced rendering.

If I override the new model’s default material with a material from one of the working faces, the problem still occurs (flat, non-textured surface, doesn’t matter WHAT material I put on the model, it won’t render properly as an instance).

It appears that the MODEL in question simply won’t render properly using instanced static meshes, but as far as I know, there is no reason a model wouldn’t work for this kind of specific case. In any case, I compared ALL of the model settings to an old model that works, and I see NO differences, EXCEPT, the new model has two material slots. ALL previously working models only had one material slot.

Can instanced rendering not handle models with multiple materials?

Can anyone suggest anything else to look at or try?

Only thing I can think of is enabling “Use with Instanced Static Mesh” in the Material Properties on your new Material Slots.

Well, your question already contains the answer to some degree. Multiple materials break the concept of mesh instancing.