I have downloaded ADE 2.0 on my Mac and purchased ebooks on line. I cannot download the books as I cannot authorise ADE 2.0 for my Mac. The help tells me to click on the info button - I can't see one on the screen the screen just shows a list of products and services when I open it.
To authorize the Mac, you need cmd-shift-U, or menu/Help/Authorize Computer.
If that goes ok, ignore the rest of this post, but there is a common problem so just in case ...
Sometimes ADE gets its registration/activation confused and in a semi-authorized state.
Uninstalling and reinstalling does not help, and indeed installation can even trigger this state.
Unfortunately, it often then gives misleading error messages about what is wrong.
A common incorrect message informs you that the ID is already in use on another computer and cannot be reused.
Another is "E_AUTH_NOT_READY"
This can often be resolved by completely removing any authorization using ctrl-shift-D to the Library screen on ADE (cmd-shift-D if on Mac).
Restart ADE, and then reauthorize with your (old) Adobe ID.
In extreme cases on the mac, the following extra step has helped some people. Navigate to /Users//Library/Application Support/Adobe/Digital Editions and drag the activation.dat file to the trash. If you are using 10.7, see Access hidden user library files | Mac OS 10.7 Lion. http://forums.adobe.com/thread/1265248?tstart=0