An unknown error has occurred app store

wagaya wrote:

Really bizarre. Hearing some people suggest that it's a problem on Apple's end is discouraging, as it suggests anything else I try may automatically fail. Yet if I can use the App Store from another user account, that suggests there has to be something lurking in my main account's Library (probably) that's causing the problem...

After running around in circles trying to get this resolved for me I finally found a (fairly easy) solution - the key point here is that the AppStore works just fine form another user account on the same computer (using the same AppleID) so it has to be something in ~/Library rather than /Library (thus ruling out the NetworkInterfaces.plist fix - which I tried and which didn't work for me).

Here is a step-by-step of what worked for me:

1. Create a new user account - let's name it "Test" - I did not make this an administrator account
2. Log into that new user account (skipping the AppleID/iCloud screen)
3. Select "Software Update…" from the Apple menu - you will be asked to enter an administrator name and password in or to check for system updates - just provide your normal (admin-enabled) user name and password
4. If you have any updates available, click "Update All" and log into the AppStore with your normal AppleID/password (this should work since you are in a new user account)
   (If you don't have any updates available, I assume that you can also log in using the menu item in the Store menu of the AppStore application though I have not tried that)
5. As soon as the download starts, you can quite the AppStore application
6. Log out of your test account and back into your normal account
7. Open /Applications/Utilies/Terminal
8. Type the following command:
   sudo cp /Users/test/Library/Cookies/com.apple.appstore.plist Library/Cookies/
9. Open the AppStore again and you should be able to log back in

What does this do? It seems that the com.apple.appstore.plist file in your normal user account has become corrupted - we use a new account and create a new one (which is interchangebale since we use the same AppleID) and move that one back to the main account with the corrupt file.

Andreas