We have noticed some problems in Garry's Mod 12 archive
Here are some most notable problems we know:
-Episode 1 probably was the only vpk that brought maps, the other games content did not come with maps. Only ai and navs.
-For the other maps, you need to install them manually.
-Gcfscape may corrupted the games files or it didn't came packeged.
-May not be working properly.
-It may not work because you're using Source SDK 2007 and the Steam IP network wasn't implemented in that application (yes application, it says launch, not play), and only local server is possible unfortunately.
-It may not work because its an old version of Garry's Mod
-You can watch the tutorial here, just three simple steps: https://youtu.be/vT-qL_ldVtw
Credits:
-Myself (NotSaying) Making the website and playtesting the game for bugs.
-firedog865: Correcting my mistakes :D
Remember, always have fun :D And if you found new bugs, please reach out! ---> https://discord.gg/UyPfGXsq