can't associate Adobe Digital Editions with ASCM files

Hey all,

I was directed here from customer support, who couldn't help me.

I am trying to open a Netgalley arc. I downloaded Adobe Digital Editions as requested, authorized it, everything seemed ok, but when I tried to download the book, I was told "Your computer cannot open this type of app." 

So I went in to settings to make sure that Adobe Digital Editions was the default app for ASCM files. It isn't even an option. The only things that come up are Adobe Acrobat and Word, and then a link to the app store, where Adobe Digital Editions is not available. 

I have no idea how to get it working. I'd appreciate any advice!

Thanks.