Apple App Store access problem
Why do I get this error message?
“An unexpected error occurred while signing in. The data couldn't be read because it isn't in the correct format."
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found the solution for this on Mac Community website:
"Remove the following files (some may not exist) and restart the computer:
~/Library/Preferences/com.apple.appstore.commerce.plist
~/Library/Preferences/com.apple.appstore.plist
~/Library/Preferences/com.apple.appstore.plist.lockfile
~/Library/Preferences/com.apple.appstored.plist
~/Library/Preferences/com.apple.SoftwareUpdate.plist
~/Library/Preferences/com.apple.SoftwareUpdate.plist.lockfile
~/Library/Preferences/com.apple.storeagent.plist
~/Library/Preferences/com.apple.storeagent.plist.lockfile
After you log back in your App store will work.
Looks like the root cause may be one of the above configuration files being corrupted. After you log in they get recreated cleanly. " arns_mac