Well, the reflection is working correctly - it just doesn’t show up very well with the default settings.
The attached image shows renders after a series of cumulative changes on the surfaces tab:
1. Loaded the rectangular shield prop into DS4.5, X-rotated it 180° so it’s face-up, selected top view and zoomed a bit. No lights in the scene, so DS default lighting. Applied the ShieldTMS(Full).duf. Rendered it. No sign of reflection.
2. Set ‘Wear Mask’ to ‘None’on the surfaces tab (SEAShieldRectangular > Shield > Masks) and re-rendered. You can just make out the reflection if you look very carefully.
3. Set specular strength to 0% (was 50% by default) and reflection strength to 100% (was 50% by default) for the Mid Texture (SEAShieldRectangular > Shield > Mid Texture > Specular/Reflection) and re-rendered. The reflections a little bit easier to spot.
4. Set the diffuse color to mid-grey, 128,128,128, (was 32,32,32 by default) for the Mid Texture (SEAShieldRectangular > Shield > Mid Texture > Diffuse) and re-rendered. The reflection is very clearly there now
Click thumbnail to see full-size image