Make sure you have enough available storage space on the drive which the workshop content is installing into. If you have enough available storage, make sure the custom mods/maps are actually installed by checking the workshop directory for BO3’s content, which is typically found by opening the game’s folder by right-clicking it from your Steam library, selecting Manage > Browse local files, selecting "steamapps" from the address bar to open it, then navigating through "..\steamapps\workshop\content\311210"

If they’re installed but they’re not showing in-game, you can try to either load the custom mod through Steam’s launch options for the game, select the custom map using console commands, or force BO3’s workshop content to refresh.
Selecting custom mods can be done through setting the game’s launch options through its properties on Steam as “+set fs_game MODNAME”, where MODNAME for a mod installed through the workshop is the numbers found by looking at its folder name in BO3’s workshop folder or by looking in the mod’s workshop.json file and looking for the value assigned to “PublisherID”; and for a mod installed directly in BO3’s directory instead use the name assigned to “FolderName”.

Selecting any map can be done by using the following console command while in the designated mode’s lobby screen: “/lobby_setmap MAPNAME” where MAPNAME is the console name of the map you’re trying to load. You can find the console name of the map by looking in its workshop.json file and looking for the name assigned to “FolderName”. Here’s an example of a command for loading a map which its console name is “zm_ccube”: “/lobby_setmap zm_ccube”.
To use console commands, you’ll need a mod loaded. If you don’t have any mods, you can set BO3’s launch options through Steam as “+set fs_game usermaps” to load an empty mod.

To force BO3’s workshop content to refresh, follow this:

1. Subscribe to the workshop content you want.
   
2. Close Steam.
   
3. Locate and delete this file: “appworkshop_311210.acf”. It should be located in Steam’s workshop directory, typically found by opening the game’s folder by right-clicking it from your Steam library, selecting Manage > Browse local files, selecting "steamapps" from the address bar to open it, then navigating through "..\steamapps\workshop"
   
4. Reopen Steam, then open the game. BO3’s workshop content should refresh upon doing so.

If you have more than about 140 custom mods/maps installed for BO3, just know that the game caps how many custom mods/maps show at once, and my previous suggestions might not work for you.

Some extra information:
Another method for loading mods which are installed through the workshop is creating a folder with the name set as its PublisherID number in the “BO3_ROOT\mods” path, and then loading that mod through the in-game Mods menu. Create the “mods” folder if it doesn’t exist.
Installing custom maps/mods downloaded through the workshop directly into BO3’s directory: https://youtu.be/ptU29D7MXhE

To force BO3’s workshop content to refresh, follow this:

1. Subscribe to the workshop content you want.
   
2. Close Steam.
   
3. Locate and delete this file: “appworkshop_311210.acf”. It should be located in Steam’s workshop directory, typically found by opening the game’s folder by right-clicking it from your Steam library, selecting Manage > Browse local files, selecting "steamapps" from the address bar to open it, then navigating through "..\steamapps\workshop"
   
4. Reopen Steam, then open the game. BO3’s workshop content should refresh upon doing so.

After doing that they are completely gone for me.

Originally posted by Yubu:

Originally posted by Hadi77KSA:

To force BO3’s workshop content to refresh, follow this:

1. Subscribe to the workshop content you want.
   
2. Close Steam.
   
3. Locate and delete this file: “appworkshop_311210.acf”. It should be located in Steam’s workshop directory, typically found by opening the game’s folder by right-clicking it from your Steam library, selecting Manage > Browse local files, selecting "steamapps" from the address bar to open it, then navigating through "..\steamapps\workshop"
   
4. Reopen Steam, then open the game. BO3’s workshop content should refresh upon doing so.

After doing that they are completely gone for me.

Following this should trigger Steam to download the mods again the moment you launch the game. Let the download finish, restart the game, then check if they’re there.

Had to resubscribe to one of the workshop maps to trigger the download.
Might be a problem on my side but it was a thing.
I'll put out another reply once it's done.
Hope they load in now.

Well my mods are back.
But they are only in the map tab, not in the mod tab.

Originally posted by Yubu:

Well my mods are back.
But they are only in the map tab, not in the mod tab.

Right-click the game from your Steam library, select Properties... > Workshop, and make sure they're marked as checked.

Originally posted by Hadi77KSA:

Originally posted by Yubu:

Well my mods are back.
But they are only in the map tab, not in the mod tab.

Right-click the game from your Steam library, select Properties... > Workshop, and make sure they're marked as checked.

All marked.

Originally posted by Yubu:

Originally posted by Hadi77KSA:

Right-click the game from your Steam library, select Properties... > Workshop, and make sure they're marked as checked.

All marked.

The only possibility I could think of is that you’re only subscribed to custom maps, no custom mods. If that’s not the case, then maybe try changing their load order from the page I described how to open earlier, or unmark them then mark them back, and restart the game after doing so. I’ve got nothing if this doesn’t work.

looks like my mods arent downloading when i press subscribe. anyone know a fix for this?