They replied that everything was fine on the part of the hosting server.
We agree that the problem is the incompatibility of the "Zino" theme (by Manesh Timilsina) and the "ARI Fancy Lightbox" plugin.
How to fix it?

The problem on aktiv-uk.ru was with MIME type configuration on web server side. Currently the plugin is disabled on the site so we can't check if MIME type issue is fixed.

Regards,
ARI Soft

The hosting refuses to admit that the problem is on the web server.
Moreover, there is a website of the energy company trigger-it.ru the plugin version 1.3.13 worked fine on it.

Today I dared to update the plugin to 1.3.18 and got the same empty windows instead of a PDF document.

PHP 8.2
Wordpress 6.7.2

rolled back to the backup site with 1.3.13

Now I noticed that on 1.1.13 there are also some PDF documents that used to open normally, but now the screen is blank. But not in all browsers, only in Opera. Chrome - open. Yandex - open. Edge - open.
Maybe something in browsers changes with the update of versions?

For example on the page: trigger-it.ru/openinfo/2025-2/

point "19в", chapter "б"


And in version 1.1.18, it becomes quite explicit and obvious as at the beginning of this post. PDF documents behave differently and unpredictably in different browsers.

I'll try experimenting with clearing the browser cache. Maybe something gets clogged. I deleted all the data from Opera and restarted it. The document began to open.

But that's not normal, is it? The visitors won't be doing this.
Mobile devices, various websites.

I will write about the results of the experiment.

I'm inclined to believe that there is no compatibility with the Zino theme. nothing helps her. No different versions of the plugin. No cleaning of the cache. What can be done with MIME on my part is not clear, on another site on the same server of the same hoster everything works on version 1.1.13. There were glitches - clearing the cache.

Tomorrow, after the backup, I will try again to update to 1.1.18 and see if the PDF opening breaks or not. And whether clearing the cache in browsers will help.

But none of this works on the Zino theme. The same wordpress, the same hosting, the same web server, the same php version