I'd also like to add that this error happens no matter what the contents of the mission are. Blank slate and fully made scenario give the same error.

I've experienced the same problem

I also am unable to host servers (non-dedicated) with the DLC enabled. Re-downloading it now, but with the DLC enabled, can't host, with it disabled, I can host just fine. I suspect these errors are connected somehow.

update: I appear to have solved the problem by opting out of the Steam client beta thing. Something about the newest beta update made Workshop services and server hosting not work properly in the game.

I'm having the same issue and I'm not opted into Steam client beta.

Same issue and I am also not opted into Steam Client Beta. I have verified all files on both tools and Arma 3 and yet the issue persists. I have tried forcing an update in Steam but none are available in case the issue existed there.

I don't have the dlc, get the same problem, tried reinstalling entire steam and arma, restarted modem, disabled firewall, nothing helps.

I have the DLC and get the same problem. Can't update any of my S.O.G. missions for anyone anymore. Hope this gets fixed soon.

I have the same problem. I had it before 19th May when i was on Steam Beta branch, but since i opted out of it things became good again. Until today.
Error started appearing today again, i guess this Steam Beta update moved into their stable Steam branch.

"Since the DLC came out" or "Since the last Arma update 2.04 came out"
when exactly did that start? So far it doesn't seem to be caused by Arma.

In T158403#2192726, @dedmen wrote:

"Since the DLC came out" or "Since the last Arma update 2.04 came out"
when exactly did that start? So far it doesn't seem to be caused by Arma.

It is tied to recent Steam update. I guess they changed their Steam Cloud API and Arma needs to update it too.

Steam support won't help me, they keep refering me to Bohemia's support.

In T158403#2192729, @Socrates wrote:

In T158403#2192726, @dedmen wrote:

"Since the DLC came out" or "Since the last Arma update 2.04 came out"
when exactly did that start? So far it doesn't seem to be caused by Arma.

It is tied to recent Steam update. I guess they changed their Steam Cloud API and Arma needs to update it too.

That sounds right. This issue started happening on May 18. The DLC came out before that so likely a Steam issue.

Same Problem for me , since the May 18 . I have désinstaled all game and steam , But the problem persist . No one know the solution ?

https://store.steampowered.com/oldnews/?feed=steam_client

This doesn't confirm the "steam update broke it" theory.

Hello Dedmen , Do you think the error came from steam? I asked support, they told me that it came from arma 3 and that they cannot do anything .

Cloud access is disabled on steam side, not our fault. We didn't do anything.
We'll get in contact with Steam and see what they can tell us...

ok thank you. These still a big problem have little more to publish or update

SOLUTION: 1) open steam console with WIN+R type steam://open/console

2. in steam console type this command: testappcloudpaths 107410

Worked for me.

Can confirm - worked for me too. Thank you for posting the solution.

Solution works for me too!

This should now be resolved via the Steam configuration, so no game update was needed.
(Steam client was recently updated to include a fix to a many year old glitch that had this side effect for Arma 3.)