If a Steam Workshop map fails to load, it may not have downloaded correctly. Zone Files | OpenAssetTools
C:\Program Files (x86)\Steam\steamapps\common\Call of Duty Black Ops III\zone\ call of duty black ops 3 zone files download
When using external zone files, you might encounter issues, particularly if you are trying to play them on custom clients like the BOIII client. If a Steam Workshop map fails to load,
: Switching your game language can sometimes cause the engine to search for zone files that do not exist in your directory. Common Zone File Error Messages you might encounter issues
Extract the files. You will typically see a folder named after the map, containing .ff (fastfiles) and sometimes a zone folder.