Most common Adobe error messages experienced on Ebook Central are listed below:

If you are receiving the Adobe Digital Editions error "E_ADEPT_NOT_READY” or "E_ACT_NOT_READY" when downloading an ebook, according to Adobe, this error occurs when the authorization information is damaged. The solution is to rebuild the activation file. For the step by step instructions on how to do this (de-auth and re-auth ADE), please refer to our support article available at:

According to Adobe, this error message indicates that you are trying to open a book that was already downloaded to another Adobe ID under the current download period.
Please refer to our support article for more info on this, available at:

If you are receiving the Adobe Digital Editions error “Unable to download. Error getting License. License Server Communication Problem: "E_ADEPT_NO_TOKEN” when downloading an ebook from Ebook Central, please contact the Ebook Technical Support to report the error. Please provide Technical Support with the Ebook Central URL for the ebook, the title of the ebook (including the Document ID or ISBN), and a screen shot of the error message.

You can sometimes get the following error message while activating Adobe Digital Editions:
If any of the following system settings are incorrect, this error can occur: You can also get the error if you don't open the file downloaded from Ebook Central in a reasonable amount of time. The .acsm files downloaded from Ebook Central have an expiration time (set by Adobe) and if you don't open the .acsm file within 24 hours of downloading it the title won't open in Adobe Digital Editions.

If you receive this error please check your computer's time, timezone and daylight saving settings, then download and immediately open the file with Adobe Digital Editions.

Other Adobe Digital Editions errors might be resolved by de-authorizing and re-authorizing Adobe Digital Editions. 

In addition please refer to Adobe's Website for more information with regards to Activation Errors at: