I have ADE 4.03 installed. The problem will occur once ADE is closed and re-opened. So you have to do the fix every time you use ADE to download a book.
1. For Overdrive - select book and click download. - pop up - select --save file.-- Under Open With select --acsm_auto_file -download acsm file to your download directory.
2. Open file explorer - go to OS (C:)--expand
---- go to Program files (x86) -expand
-----go to Adobe -expand
---- go Adobe Digital Editions and left click.
---- On right hand side of screen Right click Digitaleditions.exe.
--- Pop up menu - left click PROPERTIES
----Pop up choose COMPATIBILITY
--- at the top of the compatibility menu choose Run Compatibility troubleshooter
--- Pop up choose TroubleShoot Program
--- Pop up choose The Program worked in earlier versions of windows etc
---- left click NEXT
---- POP up -- Which version etc? Choose I DON'T KNOW
---- left click NEXT
--- POP up - Left click Test Program-
----AT THE BOTTOM TOOL BAR of the Window's Screen a FLASHING ICON will appear -- Left click Icon - a pop up will ask if you want this program to change etc. Left click yes.
3. ADE will Open --- Make sure that ADE is in the Library View -
---- Left click FILE and then choose ADD TO LIBRARY in the drop down menu.
---- POP UP---- Lower right corner choose acsm file type
---- left hand side of pop up choose the directory where you downloaded the ACSM file.
---- Highlight the ACSM file in right side of window and left click OPEN
--- this should work, but you will have to go through the whole routine if you close ADE.
I HOPE THAT ADOBE will get this fixed. With each update of Windows 10 ADE seems to get a little more flakey.