What is most likely happening is the game (or the Steam Client) is not being run with the proper Windows User Account administrative permissions - which is needed in order for the game to read/write files on your hard drive.

Ensure that your Windows User Account has the proper administrative permissions to run programs and apps. Please ensure that you are running the game in administrator mode if possible. Please visit Microsoft Support's website for information on ensuring administrative permissions: https://support.microsoft.com/contactus/

1) Run the Steam client as an Administrator
- Fully close out of Steam and restart your computer.
- After restarting your computer, right-click on the Steam icon > select "Run as Administrator"
- If that does not work, go to step #2.

2) Run Don't Starve Together as an Administrator
- Run Don't Starve Together dontstarve_steam.exe as an administrator in your game folders (Steam\steamapps\common\Don't Starve Together\bin\dontstarve_steam.exe)
- Right-click on it and select "Run as Administrator"

3) Check your Anti-virus, anti-malware, Firewall, and security settings
- Depending on your firewall, security, and antivirus settings, occasionally it may block a program that you want to access. Ensure that your firewall, security settings, and other antivirus software is allowing the game to do so. You can find more information here: https://support.steampowered.com/kb_article.php?ref=9828-SFLZ-9289

Note: You can also ensure that Don't Starve Together and your Steam client programs have both been added to your security software's or firewall's allowed/trusted programs list, so they are not blocked from being able to read/write your hard drive.
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If Steps #1, Step #2 and Step #3 do not help, please try Step #4 and these should be able to help resolve the issue.

4) Check your Controlled Folder Access settings
If you currently have Windows Ransomware Protection enabled, it may block the game from being able to access, read, or write files on the hard drive. If that is the case, you will need to allow/add the game’s .exe file (dontstarve_steam.exe) through Controlled Folder Access, in order for the game to be able to do so.

Here’s how to do this:

1) Select Start > Settings > Update & Security > Windows Security > Virus & threat protection; In Virus & threat protection, scroll down to Ransomware Protection, click on “Manage ransomware protection”

2) Check to see if Controlled folder access is ON, if it is, click on “Allow an App through Controlled folder access”

allow_controlled_folder.png

3) Click on + Add an allowed app > choose “Recently Blocked Apps” if Don't Starve Together was blocked previously or “Browse All Apps” and manually add Don't Starve Together. Each of these options will add dontstarve_steam.exe to the controlled folder access. If you are not sure where the file is located, generally it is within your Steam folders at \steam\steamapps\common\Don't Starve Together\allowed_app.png

4) Once added, launch Don't Starve Together once more.

*source:https://support.klei.com/hc/en-us/articles/360029882051-My-mods-are-corrupted-workshop-xxxxxxx-and-I-can-t-remove-them

It could also be corruption of game files. Have everyone do the following:

-Turn off auto-subscribe, if they have it on (in-game).

Then, with the game not running:

-Unsubscribe from ALL mods, on the Steam Workshop page.

-Go into the "Don't Starve Together" file/folder and manually delete ALL mods.

To do so; manually delete ALL:

workshop-<number> directories from your
C:\Program Files (x86)\Steam\SteamApps\common\Don't Starve Together\mods directory.

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After doing so, launch the game WITHOUT adding ANY mods back in, then see if you run into the same issue.

If the game still doesn't work with NO mods enabled, then it's likely another issue.

If the game does work correctly with NO mods enabled, then it's due to mod incompatibility..
this is where the process can become a lengthy one, as everyone should do the following:


Everyone can then begin the process of adding those mods back in, ONE AT A TIME, then playing for a bit together in-between adding each one.

Once everyone finds the mod(s) causing the issue, if you'd like, they can then go to the mods that have the error, and leave a comment on that mods Workshop page.

If the creator of the mod(s) causing the issues don't update them.. then there's nothing that can be done to "fix" it. Everyone will just need to disable whichever mods found that are causing the issue.. and check back in on that mods Workshop page, every now and again, to see if they've been updated.