Textures didn't come through?

Several things to look for:

Make sure the .obj file has "usemtl" statements. These appear in the face section and have the format "usemtl my_material".

Make sure that each statement is matched by a material declaration in the body of the pp2, with the IDENTICAL name used in the usemtl statement.

These will look something like:

    material Seats
        {
        KdColor 0.811765 0.811765 0.811765 1
        KaColor 0 0 0 1
        KsColor 0 0 0 1
        TextureColor 0.8 0.8 0.8 1
        NsExponent 100 ...

Lastly, be aware that props won't always take material POSES.  To make a long story short, it works best if the prop is parented before you try to apply a material pose to it.  I don't think this is the problem you describe but it is worth being thorough.