Downloading a borrowed book to devices using iOS
On iOS devices in Safari, “downloading” a lending book just saves the token file in "Files" but does not automatically open Adobe Digital Editions. This is a known problem.
Using the mobile Chrome browser automatically opens Adobe Digital Editions. This the recommended route for devices using iOS.
Alternatively, in iOS Safari, you can tap on Downloads > choose the ACSM file > tap to “Share” the file > in the list of apps, either select ADE directly or scroll right and choose “More”, then choose ADE.