I had a look at the fbx files of your provided link. The Wikitude3dEncoder displays an Error-Log after import. If you click on an error you see a more detailed description below. In this case one of the errors is "File not found:tex/Buss.tga". This means that the file path is wrong, or the texture doesn't exist. In this case the texture wasn't packaged into the fbx/wasn't packed to the download package. Unfortunately there are a lot of corrupted models out there with missing textures as in this case for example.
If you have Maya or Blender and open the fbx file there you will also see that the textures are missing. In this case you could create your own materials in a 3d modelling tool of your choice, export the model again to an fbx and import it into the Wikitude3dEncoder.
Hope that helps,
about 6 years ago
I read about choosing the right 3D model for wikitude and tried many (more than 10 !!) 3d models (In .dae and .fbx format) to convert into wt3 model but all time 3D encoder encounter an error.I have downloaded my 3D model (as an exapmle) from this link http://www.turbosquid.com/3d-models/free-weathered-ruins-3d-model/668275 that i tried to convert into wt3 model but it gives an error. What should be the solution for this 3D Encoder error problem ?