OK, that's weird. The Nieuports were already utilizing textures, so that shouldn't have been a problem.
Perhaps the issue is with the shaders.
I've just uploaded another update labeled: pfalz 1_12.zip which replaces the standard Vertex shader with the Mobile equivalent.
The original VertexLit was exclusive to Unity version 4 so it's possible it's no longer compatible with later system types or operating systems.
You can try this update. Hopefully it will work, but again, I'm not sure.