Can't add Project Thumbnails on certain page

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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?

Dear @lkcomjoo
what kind of CUSTOM JAVASCRIPT CODE do you use?
I see that something gets called.

Best!

Marius

Thank you for the quick reply.

I am unsure which Custom Java Script is used on this website. How can I find this out?

Dear @lkcomjoo
do you have code in this box?

Best!

Marius

No, there's nothing in this box.

Dear @lkcomjoo
Best is if you write me a PM and include your username, password and a link to this conversation.

Marius

Dear @lkcomjoo
I did not do it – but I would try to deactivate all the plugins you have installed.
Just to see if that is the problem.

:-D

Best!

Marius