Adobe Digital Editions app can't be found

I've bought a few books from google play that I want to put on my Kobo.  I've downloaded ADE 4.5 and run the installer successfully but when I click on the app I get the message "Adobe digital editions app 4.5.app" can't be found.  I've tried uninstalling and reinstalling.  I've tried installing an older version but I can't get it to work.  I've looked online but I can't find a resolution to this issue.  I'm running OS X 10.11.6.

Does anyone have any ideas?

Thanks