Please see my signature. You'd probably find the solution with a search of the forum, but if not, we need more information for an appropriate response.
My problem is to have the Profile Gallery working properly on my site.
Today I have my Display Format as Thumbnail Lightbox but that doesnt work, when I click on an image on my profile gallery it opens a new window and not the lightbox to display the images.
I dont know where is the problem to fix it.
I've seen many posts here but none with a proper and definitive solution.
It's likely a problem with your template or another extension. Does it work with a default Joomla template? Try enabling the Joomla legacy plugin if it isn't already. Which PHP version (x.x.x)?
Although you aren't using the latest PHP, I doubt that's causing the problem. As far as changing the template, it would only be for a few minutes to check whether it works or not. Changing it won't affect content... just the look.
If you won't try the default template, we can't rule that out, so the only other alternative is taking down each CB plugin and Joomla extension until you can determine if it's another extension causing it instead of the template.