I can't add Project Thumbnails anymore on a certain page (on all other pages on this website it works). When I click on the button "Project Thumbnails", nothing happens.
(As you can see in the picture, the button turns dark grey when I click on it, but the pop-up with the project thumbnails does not open.)
I use Safari and Chrome and have the problem in both Browsers.
Operating system: macOS Mojave (Version 10.14.3)
URL where problem is experiences: http://dace-project.com/news/
(It works on the other pages, just not the news page. It used to work and then stopped working there.)
What can I do to fix this?