Followed official tutorials and some 3rd party, used provided base/decal presets.
Materials/Textures doesn't work in CS:GO maps.
Props/Maps etc works fine.
They show in HammUEr:
i got the same problem
That looks like a base material problem.
Open your base material and check to see if it says anything about errors there, there might be a broken texture reference there you have to fix before it'll actually render.