Yep. This is one of the slight pitfalls with using meshes with custom shaders. The authors of shaders sometimes do not abide by the standard variable names Unity and Beast expect. Without knowing more about that material, you could just use the standard diffuse shader. Then, use a diffuse texture in the diffuse slot. @p6r has more experience with this pack and might be able to suggest another shader or workflow. You'll also want to add a mesh collider to the converted mesh so you can walk on it.