If it's open, quit iTunes.
Click your desktop to make sure that you're in Finder.
From the menu bar at the top of your computer screen, choose View > As Columns.
From the same menu bar, choose Go > Go to Folder.
-
In the window that appears, type the phrase:
/Users/Shared/adi
Click Go.
If you see a message that says "The folder can’t be found":
- Check to see if /Users/Shared exists by going to /Users/.
If you see a Shared folder, but it has a red circle with a minus sign on it:
Click your desktop to make sure that you're in Finder. Then, from the Go menu at the top of your computer screen, choose Utilities.
In the Utilities folder, find Terminal and open it.
Type this command in the Terminal window:
sudo chmod 1777 /Users/Shared
Press Return.
When prompted, enter your administrator account password. Then press Return.
Quit Terminal.
If you don't see a Shared folder
Click your desktop to make sure that you're in Finder. Then, from the Go menu at the top of your computer screen, choose Utilities.
-
In the Utilities folder, find Terminal and open it.
The next step requires you to enter commands in Terminal to modify permission settings. If you're unfamiliar with Terminal and UNIX-like environments, be cautious. If you enter incorrect commands, you might lose data, or your system software might become unusable. If you don't change permissions exactly as shown, you might reduce system security or expose private data. This step requires a non-blank admin password.
Type this command in the Terminal window:
sudo mkdir -p/Users/Shared/
Press Return.
When prompted, enter your administrator account password. Then press Return.
-
Type this command in the Terminal window:
sudo chmod 1777/Users/Shared
Press Return.
Quit Terminal.
If /Users/Shared/ exists and you can open it
Click your desktop to make sure that you're in Finder. Then, from the Go menu at the top of your computer screen, choose "Go to Folder."
-
In the "Go to the folder" text box, type:
/User/Shared/adi
From the menu at the top of your computer screen, choose View > as Columns.
Find the adi folder and drag it to the trash. You can also click it then press Command + Delete on your keyboard.
When asked, authenticate the password for your Mac.
Open iTunes and try to sign in.