I have the same problem, in my case I am trying to open the file on my android tablet. I downloaded the .acsm file on my tablet, then installed Bluefire Reader application on my device. Opened the Bluefire Reader and authorize with the same Adobe ID with which I am opening the book on my PC (But on adobe digital editions). But when I am clicking on the .acsm file it is showing can't open the file. Then I installed the adobe digital edition app on my tablet and authorized it with same adobe id, now when I am clicking the .acsm file it is opening the adobe digital reader but nothing happening. I mean book is not opening it is only opening the adobe digital reader app. I am so frustrated with this tried hundreds of times now.