The link at most libraries (and for that case book stores) for the ePub actually downloads an ACSM file; this can not be loaded onto Kobo (or calibre for that metter).
Rather the ACSM file is a control file for ADE that will download the actual book, and associate it with the ID associated with that install of ADE.
From there the book can be transferred to an eReader that has been associated with the same ID that downloaded the eBook.
See
https://www.mobileread.com/forums/sho...d.php?t=189519 for a document describing this.