Also... try importing this file: "grouped_capsule.zip" (at 1000 scale factor) and use the "Don't Split" option... you should get one mesh object, with several groups set up, along with several materials.

Once it's imported, try exporting it.  If that works, then it should be a good example of how to set up your mesh.  You can double-click on the Group Tag to see that the group selection tags are over in the right-hand side and the ones in the left-hand side are material selection tags (so they don't go over to the Selected side).

Also note that the materials are given the same name as the selection tags for each material (that shouldn't be required, but it's easier to keep track of things that way).  Also, if you click on each material over in the Object Manager to see it's properties, they are all restricted to the selection tags that were set up for them.

The last thing to check is to be sure to NOT use any of the special 'Shaders' in your materials (like Danel, Cheen, Fog, Mabel, etc).  Those are not portable and not handled by Riptide.

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