1. Vito the workshop and then subscribed and uncheck all of your subscribed addons
2. Remove all the files from the addonns folder
3 Goto good - options - multiplayer - download all custom files
Head to fastdl.limelightgaming.net/maps then download the file there. Replace it with the one in your maps folder and you should be set. If this doesn't work, please let me know.
The map file is located here:
fastdl.limelightgaming.net/maps/
and should be placed into "C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\maps"
Please do keep us update whether this resolved your issue.
Source :https://limelightgaming.net/forums/thread-12359.html - Guide Section - Helped a lot of people.
Ensure that you have no addon that may be overwriting the map file.
Make sure that your definitely placing it in the right GMOD installation. Some people find they have two.
You can also try placing it in \garrysmod\download\maps, to overwrite any other maps you downloaded from other servers.
Forgot to move to archive.