Same problem here. When changing the shortcode in “Select a shortcode”, it tries to redirect to the wrong URL.
In my case, I have WordPress installed in a subfolder /wp folder, but WordPress takes care of the site root. In other words, site is in / and admin is in /wp/wp-admin/.
The plugin redirects to:
when it should be:
Maybe the problem is a hardcoded call to /wp-admin, regardless of where the current WordPress installation is? Or maybe you’re taking the root path from the *site* URL and not *wordpress install* URL?
Hope this info helps.