Mods not working.

[Chemy Chem]

So I recently helped a friend download a mod by signing into his profile and downloading it for him as he doesn't have the fastest connection in the world. Note that before that, all my mods were fine. But when I signed back into my profile and booted up L4D2 and check my addons list, I noticed alot of my mods weren't showing up. I thought they uninstalled but when I went to go subscribe to it, I noticed it was already subscribed. In fact, all of the "missing" mods were subscribed to. Please help?

[Chemy Chem]

Edit: In the console command menu, I get this message. "An error occurred while attempting to download a file from the UGC server!"

[AlwaysToast]

You described mods & the workshop, working exactly as Valve designed them to work.

Your list of subscribed mods is part of your account. The Workshop file where all the mods are stored, is on your computer. Your computer only has one Workshop file, so it can only keep track of one set of mods in this system. It keeps whoever's account is logged in. If you log into two different computers, your account knows which files you are subscribed to, but each computer has to download the file on each computer individually. So letting your friend log in on your computer doesn’t help get the file on their computer.

If someone else logs into Steam on your computer, it looks at that person’s mod list, and deletes anything in the workshop file they shouldn’t have, and “downloads” any mods they should have. If you log back in, it looks at your mod list, deletes any mods you shouldn’t have, and downloads any mods you should have.

Your Mods aren’t “Missing.” Letting someone else log into their account, on your computer effectively deletes all your workshop file. That's not a mistake, that's how the system is designed. Your computer will download them if you turn on L4D2 (if there are no problems with the workshop at that time). There are many posts by people who share a computer with someone complaining about this system.

The workshop has effectively a 2 step process for downloading mods. When you first subscribe, it says “downloading” but it is not necessarily getting the whole mod. When you start the game, it goes “oh we need all the mods now” and actually starts downloading the files you need. It downloads them in the order you subscribed to them. This is indicated by the 4 icon with the spinning red mark near Addons on the main menu screen. Until that icon goes away, all the mods are not downloaded, so you can’t use whatever is not there. If the workshop is down or having problems at that time, you are out of luck, until the workshop is fixed.

If you want your files permanently on your computer, you have to move their file location. This fix assumes your using a PC, I don’t know if the file path is different for Macs.

Subscribe to mod(s). Let it download. Start up L4D2 to make sure it’s actually completely downloaded and available. Then turn off L4D2 and move all your files down one level from:
/Steam/SteamApps/common/Left 4 Dead 2/Left4Dead2/addons/workshop
To
/Steam/SteamApps/common/left 4 dead 2/left4dead2/addons/

Then unsubscribe from the item (so it doesn’t keep downloading into the workshop file). They are now on your machine, where the Workshop can’t mess with them.

You’ll have to repeat process for items whenever they are updated, if like for Maps, you need to have a matching version with someone else.

Or complain bitterly to Valve until they fix how the Workshop works.

[FringeDweller]

I found that I didn't need to go through any of that to fix the issue. I fixed this by going into my Steam/userdata/L4D2#/ugc and deleting all of the files from "referenced", "download", and "temp". After that I started Left 4 Dead 2 and everything downloaded perfectly and runs fine. This might just be a fix for me but I figured I would put this up since it took me forever to figure out and no one seemed to have a valid working solution.