If you are trying to authorize your computer with a new ID you should first deauthorize your current ID. To do this press Ctrl+Shift+D on Windows (Cmd+shift+D on Mac) (You should be in the library view for this to work). Click "Erase authorization" in the dialog box that pops up.
To authorize your computer with a new ID you can now Click on Help-> Authorize computer (or alternatively press Ctrl+Shift+U on win or Cmd+Shift+U on Mac) and enter your authorization details.
Thanks very much. This worked.
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