How to fix the problem of being unable to upload mods and or blueprints to the Steam workshop.
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If you get the "Failed to publish" or "Error during Publishing/Uploading" message in-game when trying to upload either a new Mod or Blueprint/World save, or even upload an update to an existing Mod/Blueprint/World already on the Steam Workshop, then this is the thread for you!

This First step of the process might not be needed for this, However this prevents the issue from happening again in the future, and especially if you're a Mod maker, and or you plan to upload lots of Blueprints/Worlds, then this would be the best course of action to take, coming from experience myself.

1. Disable the Steam Cloud for Space Engineers on the game side of things and not the whole Steam cloud, that way your other games won't be affected, so to do that: right-click "Space Engineers" in the Steam Library and click on Properties.

2. Then go to the "General" tab and find the "Steam Cloud" section which is in the middle area of the window that pops up and make sure the checkbox for the Steam Cloud Saves is disabled/ unchecked.

Now that the easy part is done: (whew)
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1. With Steam running in the background and Space Engineers not running, navigate to the folder found here: Steam\userdata\Random-Numbers-Here\244850\

2. Move everything out of this folder and into another one(desktop folder or any folder outside of this one would be fine for the time being, or simply delete them.(They are really not needed at all, because if Steam wants to re-sync them, it can do it automatically once you re-enable the Steam Cloud Saves option in the game properties menu of Steam.

2.5^- Clear or relocate the folder called- "remote" and also the file named- remotecache.vdf, as those two are very crucial to fixing this issue.

3. Once that is cleared out, Reboot Steam and then start Space Engineers and try and upload a mod and or blueprint.

4. That will fix the issue with not being able to publish/upload new content to the Steam Workshop.

Important Note #1 - Please keep in mind that due to a change with the Steam Workshop any thumbnail OVER the 2 MB limit will fail to upload every time, and as a result you will have to shrink the file size, for my mods I use a JPEG file because it has the best compression and keeps the image quality the same and also keeps the file size below the 1 MB limit, For reference I set the image resolution to 1920x1080 size.

Important Note #2 - Sometimes for thumbnails with lots of detail in the images the 1920x1080 resolution size can be too big and will result in the file size being over the 1 MB limit once saved as I have found with some of my mods.
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