Maybe that device is not supported by ADE, but appears to work for DRM books.
You will probably still need ADE to open the .acsm token file and download the excrypted DRM .epub file; as you have already done.
From the user manual http://download.pocketbook-int.com/623/ug_22.08/User_Guide_PocketBook_ 623(EN).pdf page 77, Adobe DRM, it appears that you can register your Adobe ID on the device directly. You will just need to do this once, using the same Adobe ID you used to authorize ADE.
Then load DRM .epub files from the computer to the device using file manager (Windows Explorer, Mac Finder) as on page 16/17 of the manual.
The .epub files are probably in the 'My Digital Editions' subfolder of your 'Documents' folder.
