ePub book won't open

OK: This problem has been going on since Dec. 2015, and the issue is, as the discussion header says, "Not Answered". The suggestions from the Community point to a variety of slash-and-burn directions (e.g., you must deauthorize your whole ADE setup and remove a Library file). Is it because ADE is a "free" (but essential for using certain document files) app that nobody at Adobe has stepped in and tried to find the kinks in the code that may have led to this impasse?

Success!!!!!

None of the prior steps helped me at all.  However, what I just did that worked was to delete ALL versions of ADE on my computer and reinstall version 4.0.

I had updated from v3.0 to v4.5.2 to deal with the ASCM files type but got in the same endless loop of failure to authorize or failure to connect to authentication server, both errors (falsely) suggesting I was not connect to the internet.

The registry editing, DE-authorizing/re-authorizing, shutting down windows firewall/Norton antivirus etc. just cycled me through these error messages without solving the problem.

I don't even know when v4.0 was downloaded or if it was automatic at some point, but by uninstalling v3.0 and v4.5 and selectively installing v4.0 everything worked the way it should.

I must say I found the chat people with whom you connect when you click the Help tab in ADE was worthless (actually worse than worthless since the snarkily pointed out it was free if necessary software and therefor not supported) and the Forum articles simply cycled me through useless and sometimes scary (deactivating all my PC's security features) steps without resolving the problem.

V4.0 works as it should.   Now I just have to figure out how to assure it will not auto-update and put me back in server failure hell.

Hope this helps others.  Good Luck out there...

Macintosh:

1. Open Adobe Digital Wditions.
2. Press Command+Shift+D to deauthorize Adobe Digital Editions.
3. Select Erase Authorization.
4. Click OK and quit Adobe Digital Editions.
5. 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 library files | Mac OS 10.7 and later.
6. Open Adobe Digital Editions and reauthorize.

Windows:

1. Close all applications.
2. Choose Start > Run.
3. In the Open text box, type regedit and then press Enter. The Registry Editor opens.
4. In the left pane of the Registry Editor, locate the following registry key: HKEY_CURRENT_USER\Software\Adobe\Adept
5. Select the Adept key.
6. Choose File > Export.
7. In the Export Registry File dialog box, select Selected Branch under Export Range. Enter a name and location for the backup registry key, and then click Save.
8. Right-click the Adept key and choose Delete.
9. In the Confirm Key Delete dialog, click OK.
10. Close the Registry Editor.
11. Open Adobe Digital Editions and reauthorize.