I reset the password several times thinking something was wrong though the password always worked on the iPad. I can log in to several places using the Apple ID except the App Store on my Mac. I started getting the message when I was trying to update some pre-installed apps. I have signed out and tried to sign back in. I keep getting the message: An unknown error has occurred.
iMac, Mac OS X (10.7.5)
Try deleting App Store cookies ...
Quit the App Store if it's open.
Now open the Finder. From the Finder menu bar click Go > Go to Folder
Type or copy/paste: ~/Library/Cookies
Click Go then move the com.apple.appstore.plist file from the Cookies folder to the Trash.
Launch the App Store. From the menu bar click Store > Sign In
Thank you for your tips. I'm still getting the same issue. I have a similar problem with trying to login with the iCloud. I went to iCloud.com and logged in just fine, but I can't with my Mac.
My Apple ID credentials will work on everything except the Mac App Store. Please help!
