Hi, that happens when we enable the in-game Steam cloud to create "Cloud Blueprints", that option is not made to save at all and give this kind of problem when full..

Hav you tried the other Pin shared by a SE Modder in general DIscussions Forum ?

This other pin :
https://steamhost.cn/steamcommunity_com/app/244850/discussions/0/3192489172307109616/

Hi Dan, I have tried those steps, and someone from Steam gave me a plan to try which has also failed.

1. Make sure the game is installed, it needs to be installed for the files to be found.
2. Disable cloud functionality for the game (right-click the game in your library -> Properties -> General -> Untick "Keep games saves in Steam Cloud for Space Engineers")
3. Navigate to the account's data page for your cloud saves at:https://steamhost.cn/account/remotestorageapp/?appid=244850
4. On this page, you will see each file currently in the cloud for your account for this game. These files can be located at: [Your Steam Installation Directory]/userdata/39440446/244850
5. Navigate to the location for the files on your computer and delete any files you wish to remove from the cloud in that folder and any sub folders.
6. Now, launch the game and create at least one new save file.
7. If that was successful, close the game and re-enable the cloud functionality for the game.
8. When you launch the game again, you will be prompted by a cloud conflict window asking you to pick between two options. You want to keep local files by selecting the "Upload to the Steam Cloud" to overwrite your older files.
9. Now the data for this game should be reset. Note that in some cases the cloud files may have been overwritten successfully without a cloud conflict window appearing. You can check the account data page again to see what is now stored.

I have tried that plan 3 times with no success.

All is on default on my side, so Steam app settings on default that is cloud enabled in there and default for SE Game so cloud disabled in game from the "Options" button in main game menu
= All good this way.

Oh! Maybe try changing the Steam Download region will help, it's a new thing that started to happen since a few weeks, read the last post so #12 in that other Pin :

Forum/Community workaround(s) 📌
https://steamhost.cn/steamcommunity_com/app/244850/discussions/6/3464975177698306889/

I tried changing my region and that had no effect.

Looks like the Workshop is not working for you anymore.

You may contact Steam Support and the SE Programmers to see if they have other solutions for you to try.

Steam Support is in "Help" on top of your Steam app.

+

How to have a SE Programmer helping you :

-> Click "Submit Bug" or "Request help" on the Support Portal to have a SE Programmer testing the bug for you and be able to chat with you.

https://support.keenswh.com/spaceengineers/pc
(create "Bug report" or "Request help"(Private) or "Feedback"(Petition) on the Portal)