This is how I manage to play WLA foultless:

1. Subscribe to the WLA mission in Steam Workshop
2. Run the mission once and leave the mission again (so it can create any save files or anything)
3. Quit Arma 3 and subscribe to the WLA Sound mod in Steam Workshop
4. Run the Arma 3 launcher, go to addons and let the launcher install the sound mod addon
5. Tick the box to enable the mod and start the game
6. Start the mission and it should work (at least for me)

Hope this was any help!

Sorry, I forgot wrong text into the mission. WLA Sound Addon isnt up to date currently in workshop since addon uploading dosent work. BIS is working on that.

Before that you need to download/install the addon manually here:
https://www.dropbox.com/s/78e2wypdx0ja5p9/%40SaOk.7z

When placing the @SaOk folder in arma3 folder make sure the @SaOk isnt doubled. Should look arma3\@SaOk\addons. In arma3 launcher use @SaOk mod parameter and make sure the workshop addon is disabled.

Managed to create new page for the addon in workshop:
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=422592108

Remove the old workshop wla sound addon if trying it. :)

Okay so I'll try using this new one with the externally downloaded mission version. The workshop mission version is still outdated as the description says right?

Oh and by the way one of your links is wrong. In the above Workshop page for "WLA Addon" there is a link to the SP mission page. This link actually takes you to the old outdated sound mod.