Probably an example of wrong error message from ADE. Most of their error messages are just confusing, but they like to throw a misleading one in the mix sometimes to keep users on their toes.
It is probably semi-authorised.
Try ctrl-shift-D (cmd-shift-D on Mac) while running ADE in Library view, to remove any existing authorization or semi-authorization.
Restart ADE.
Try again to register with your Adobe ID.