I get an "E_ADEPT_REQUEST_EXPIRED" when trying to authorize my Adobe ID.

This error is caused by one of, or some combination of, the following three system settings:

1. Incorrect clock time.
2. Incorrect date.
3. Incorrect time zone.

When you download a PDF or an epub, the Adobe activation records timestamp information from the Adobe activation server. This information is stored inside the book. When you attempt to open the book, this information is compared to your current system information. If your system has an incorrect time/date/time zone, then the activation server disallows the request and you cannot read the book.

Carefully check the machine's system time, date, and time zone to be certain they match the time/date/zone when you purchased the PDF or epub. In most cases this will resolve the error.

NOTE: For Android users, we noticed the problem is often fixed by turning 'on' Automatic Date and Time.