Adobe digital editions stuck on 'downloading content' when adding acsm file to library

Currently using the mac 4.5.11 desktop version. Trying to read an ebook from the dawsonera server provided from BMA library (online medical textbooks). The ADE library fails to sync with my ipad so I've downloaded new links for the books. Library opens and authorises fine. Download starts and appears to complete (full bar) but then never actually opens? Perhaps the app crashes (see picture). 

I've uninstalled, turned off my laptop, re-installed, downloaded new links... nothing works. Please help! Really need to study 😧