I seem to have found another easier workaround to sign in to the Mac App store.
At least it works for me and does not require to create a new user. Here it is :
- SIgn off the Mac App store (if you were signed in with another Apple ID)
- Leave the Mac App store open
- Quit iTunes and iBooks if they are running
- Open Safari, and go to Preferences/Privacy
- Choose to block cookies "Always"
- Click on "details" under "Remove all website data ..."
- Search for apple.com; select the "apple.com" line then click "Remove", then click "Done"
- Quit Safari
- Open Activity Monitor (search for it using Spotlight or find it in the Applications/Utilities folder)
- In Activity Monitor, search for "storeagent". You should find "storeagent" and possibly "ibookstoreagent"
- Select each of them and force quit them (using the X in the toolbar if you are using Mavericks)
- In the Finder, go to the ~/Library/Cookies folder (go to ~/Library using the "Go" menu while pressing Alt then open the Cookies folder)
- Delete everything in the ~/Library/Cookies folder and empty the trash.
- Go to the Mac App Store and sign in. This should work. You can press Esc if asked for your username and password a second time.
- Go to Safari, then Preferences/Privacy
- Choose to block cookies "from third parties and advertisers"
- Go back to the Mac App Store. You should be able to use it "normally".
Some steps might be overkill, but it seems to work for me now.
I have one Apple ID without problem. But each time I sign it using it, then try to use my "problematic" Apple ID, I cannot sign in, unless I do these steps.
Please tell me if this works for you. (I'll send a bugreport to Apple probably tomorrow; knowing if this works not only for me would help).
Thanks in advance,
Jérôme.