I also have this issue. I narrowed it down to being a problem with permalinks.
If you set them to “plain” (https://www.siteurl.com/?p=123) archive links work fine, but as soon as you set them to anything else (like https://www.siteurl.com/%postname%/) it doesn’t work with viewer=”mini”, viewer=”presentation” or viewer=”window”. However the archive list links do work with viewer=”no”, where links post to issuu.com.
So until the plugin author fixes the issue you have 3 options:
- Set permalinks (in wp settings) to “plain”
- Set viewer=”no” in plugin shortcode
- Do a quick hack of the plugin. Edit issuupress.php. Search for
if($viewer===’no’){
and replace no with mini or whichever viewer you wish to use.