Hi Cassius, sorry to hear you are still having problems.
Q) Is this on a purchased version or free version?
Q) Do they appear in the Player?
Other users have had this problem before, but we just don't get enough information to be able to try and fix it.
Can you send the log files from the Win32 or Win64 release folder depending on what you are running as they may shed some light. Last i looked into this, i though it may be the shaders at fault not generating.
Q) What PC specs are you running. CPU, RAM, GFX, Windows OS etc...
You can try clearing your resources to see if that helps. This can be done by going into the Installed folder and looking for:
"Skyline/Data/Resources"
Delete all but the "SkylineBaseResources" file and try reloading the engine again
Gen2 skyline is coming along quick, currently there is no veg system, but it will be added into the engine as its a necessity.