Good morning,

Site with Joomla 3.8.1

I have installed Simple Image Gallery Free Plugins on test.eurocoibent.it/index.php?option=com_content&view=category&layout=theme3017:category&id=39&Itemid=257

As you can see, the plugin does not work properly when you open the lightbox.

I tried installing the plugin on a clean Joomla 3 installation with the native template and working properly.
It is clear that the template that I chose uploads to libraries that conflict with the form.

Please help!

you might try jquery easy plugin from the JED after you check to be sure K2 Options have jQuery set to load
a goo explanation is here
extensionsforjoomla.com/documentation/how-to-fix-javascript-jquery-conflicts-joomla