Insertion fails

Hello dear Joost,

Thanks for sharing your work. I would love to get your attention on my problem: I can’t figure why your great software stopped to work on my MS-WP 4 installation as I just recently noticed,… maybe due to a plugin update incompatibility?(Everything looks OK except for the insert into post button on my aquaradius.fr site…)

my plugins are

Background Manager
Better Search
CKEditor for WordPress
Easy Google Fonts
Enable Media Replace
Google Analytics Dashboard
Google Sitemap by BestWebSoft
Jetpack von WordPress.com
Media Rename auswählen
Meta Slider auswählen
Meteor Slides auswählen
Multilingual Press Free
Network Shared Media
Prepare New Version
Shortcodes Ultimate
WordPress MU Domain Mapping
WP Super Cache

best regards
C.J.

https://wordpress.org/plugins/network-shared-media/