FancyBox installed & activated but not working

Hi, I’m a newbie and am not sure if I’m doing something wrong.

I’ve installed the FancyBox plugin and activated in my WP. I don’t see any recognizable changes made to my existing lightbox gallery which is just a WP generic window (no frame, no titles) popping up with just a close button on the upper right and the left/right arrows.

I read other questions here and have done everything suggested: deactivated plugins that may have interfered (e.g. image slider); emptied the cache and refreshed many times; reverted the plugin setting to default; made sure that the plugin is uploaded to the folder /wp-content/plugins/ directory. etc… but absolutely nothing happens.

Should I deinstall and re-install again? What else can I do?

https://www.ads-software.com/extend/plugins/fancybox-for-wordpress/