You need at minimum Metamod:Source v1.8.1 and Sourcemod v1.3.2 installed on your GMOD server.
Current versions are at Metamod:Source v1.8.2 and Sourcemod v1.3.3.
And you also need the files
in this .zip file.
The .zip files contains updated gamedata files to enable Sourcemod to work with GMODs news engine.
It has 2 folders & a subfolder in each directory and 5 .txt files.
unzip the file and you will have 2 folders called core.games & sdktools.games.
In each of the directorys there is a custom folder that contains the updated Engine Information.
Upload the core.games & sdktools.games directorys to orangebox\garrysmod\addons\sourcemod\gamedata
You already have 2 folders in there called core.games & sdktools.games.
Don't worry about that as nothing gets replaced.
The updated files are placed in a subfolder called custom, as if you replace the "default" and wrong files GMOD then Sourcemod will just re-download them.
After doing the above you should have it like this.
orangebox\garrysmod\addons\sourcemod\gamedata\core .games\custom with 2 .txt files
orangebox\garrysmod\addons\sourcemod\gamedata\sdkt ools.games\custom with 3 .txt files
Having the correct MM:S and Sourcemod with the updated gamedata files will enable sourcemod to run with the new engine.
Or if you wish, instead of installing SM v1.3.3 and the above files from the .zip.
Install the
latest version of Sourcemod v1.4, as it has the updated gamedata files for GMOD with it.