If you're experiencing this error message it doesn't mean your game is already running, the actual message itself is incorrect. It means The Sims 4 cannot access the Electronic Arts > The Sims 4 folder to load your user data when you attempt to launch the game.

This is essentially a permissions issue which can be resolved based on your setup:

- If you have just installed or reinstalled the game
- If you have iCloud Drive enabled and it is syncing your Desktop & Documents folders
- If you have recently updated your Mac or the game
- If you have moved your Electronic Arts > The Sims 4 folder to an external drive and created a symlink in your Documents folder

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If you have just installed or reinstalled the game:

You would have been prompted to allow The Sims 4 permission to access the Documents folder, this is security built into macOS. This is so it can access the Electronic Arts > The Sims 4 folder in your Documents folder, if one already exists, or create a new one if it doesn't exist. If you clicked Don't Allow when prompted the game cannot read and write to the Documents folder, resulting in the error message.

Fix - Open System Settings > Privacy & Security > Files and Folders (you will need to use an Mac Administrator account to access this) and enable access to the Documents folder by clicking the toggle on:

If you do not see this option open System Settings > Privacy & Security > Full Disk Access (you will need to use a Mac Administrator account to access this). Click the + in the bottom left corner, below the list of apps. A Finder window will open to the Applications folder. Navigate to where your game is installed, by default this is Applications > EA Games, click on it and then click Open. It will now be added to the Full Disk Access list. Make sure it is toggled on. Whilst giving the game Full Disk Access isn't ideal, and shouldn't be necessary, it is a quick and easy solution to fixing the error message and the game is signed and notarised by Apple.

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If you have iCloud Drive enabled and it is syncing your Desktop & Documents folders:

This is a really common cause of this error message and is as a result of your Mac storage being full resulting in iCloud pushing the entire Documents folder to the cloud. The game cannot see the Documents folder and its contents because it is not local on your machine, therefore it cannot access the Electronic Arts > The Sims 4 folder to load user data at launch.

Fix - Open System Settings > Apple Account > iCloud > Drive and disable the Desktop & Documents folders syncing. Be aware of the effect this will have if you use multiple Apple devices to access these folders:

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If you have recently updated your Mac or the game:

Sometimes permissions can go awry after updating the OS or you have been prompted to change settings after updating and inadvertently clicked the wrong thing.

Fix - check all of the applicable settings in the instructions above

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If you have moved your Electronic Arts > The Sims 4 folder to an external drive and created a symlink in your Documents folder:

There can be multiple reasons for the error message when a symlink has been set up but they are all caused by the game not being able to access the Electronic Arts > The Sims 4 folder:

your external drive is not plugged in and properly mounted. Check the drive is plugged in and showing in Finder/on your Desktop.
your symlink is broken. This can be checked by looking at the symlinked folder in your Documents folder. If the icon is a white file and not a folder it is broken. Trash it and recreate the symlink in Terminal. If you have further issues refer to the dedicated symlink thread opening post.
the game does not have access to Removable Volumes (external drives) in System Settings > Privacy & Security > Files and Folders. You would have been prompted to give permission when launching the game for the first time after successfully creating the symlink and maybe denied it. Give the game access:
you have iCloud Drive syncing your Desktop & Documents folders to the cloud which does not work well with the symlink. Disable it (see above for further instruction).
your external drive has not been ejected properly multiple times resulting in the OS changing the mount point. Check Disk Utility and rectify, see the dedicated symlink thread opening post for further instruction.

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If you're still stuck a really quick and easy way to resolve this is to create a new Administrator account on your Mac and play the game in that account. When you first launch the game in that account you will be prompted to give all the necessary permissions for the game to access the Documents folder - make sure you allow it 😊