success. ADE 4.0 is to be avoided. It crashed after my solution.
The solution is trash the activation.dat preference file.
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.
I reinstalled ADE 3.0 and life is good.
The Error getting License. License Server Communication Problem: E_ACT_NOT_READY
on yosemite was bogus.
Thanks, I have the same problem and will try your solution