I can't load some dae. files in Model Editor

[Rapture]

What 3d modeling software are you using?

If your using Maya/3Ds, make sure you have a material assigned to your model before exporting. (You may need to look up tutorials on how to do that yourself)

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If you're using Blender, the same thing applies. But when you do "File > Export > Collada.dae" their are some less than noticeable optimal options on the far bottom-left side.

Make sure under the "Export Data Options" tab, that the "Selection Only" is checked on. (Make sure you only have the model that you want to export, is selected also!)

And in the "Texture Options:" below, the "Include Material Textures" is checked on.

(Only applies to Blender!)
I circled the two spots because this will determine what the "CustomModel.mat" file will be named, it's one of the two and I just got into a habit into naming both the same.

Spoiler below!

The two options you have to check on.

Spoiler below!

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You said "The custom models work on other people.", do you mean that you have given your model out to others for testing and they report all green?