For the Error : E_auth_not_ready.
Follow these steps,
1. Launch Adobe Digital Editions
2. Keeping ADE program active on your screen, Hold Ctrl+Shift+D keys.
- you will get a prompt window to Erase Authorization (ADE 2.0) & Deauthorize (ADE 1.7.2)
- Deauthorize ADE and Re-launch it.
3. Navigate to Help > Authorize Computer (in ADE 2.0) & Library > Authorize ( in ADE 1.7.2, usually you will be prompted to authorize when you launch the program ) .