The issue is with your theme assuming that a call to “tooltip” is a call to “Bootstrap Tooltip”, but is not including the corresponding files for it.
Photonic has inbuilt capabilities to support tooltips – it uses a custom 2KB vanilla JS script instead of what comes with Bootstrap or JQuery, thereby eliminating the need for heavier libraries (Bootstrap is 116KB). The way it works, though, is that if your theme is forcing Photonic to use a different tooltip, Photonic will use it. In this case Photonic is being told by your theme to use Bootstrap Tooltip … but is not being given the files for it! If you look at your JS console you will see this error:
Uncaught TypeError: Bootstrap tooltips require Popper.js (https://popper.js.org)
The error is preventing some critical scripts on Photonic from being executed, resulting in blank galleries.
This is in all likelihood a bug with your theme, as it is not including the files required by some of the other files that it is bundling (see here: https://themes.trac.www.ads-software.com/browser/minimal-portfolio/1.0.7/assets/js/bootstrap.js – the file is missing the Popper.js file).
I can give you a workaround that might work – switch Photonic to use a different title style either via the options (Photonic → Settings → Generic Options → Native WP Galleries → Thumbnail Title Display, which by default has the “JavaScript Tooltip” selected) or while building the shortcode. I cannot guarantee that it will work since Photonic is finding that your theme has a “Tooltip” function and is trying to default to it, but then the theme is missing a dependency.
I would suggest that you report this issue on the theme’s support forum, because any plugin that is trying to use a tooltip is likely to be tripped up by the theme’s missing file. E.g. If a plugin is using jQuery Tooltip, but is being forced by the theme to use Bootstrap Tooltip, that plugin will face the same error.
