Gallery data is missing

Hi Alan,

Thank you for reporting this.

The “Gallery data is missing” message means that the frontend script is running, but the gallery data expected on the frontend page is not available. This can happen for different reasons, including theme behavior, another plugin modifying block output, cache/optimization tools, or changes in the WordPress environment.

At this point, I cannot confirm that this is a bug in the SimpLy Gallery Block plugin itself.

Since the gallery is visible in the editor but not rendered correctly on the frontend, please first test the site environment by doing the following:

1. Temporarily switch to a default WordPress theme, such as Twenty Twenty-Four or Twenty Twenty-Five.
2. Temporarily disable all other plugins except SimpLy Gallery Block.
3. Clear all cache, including browser cache, site cache, CDN cache, and any optimization/minification cache.
4. Create a new test page with only one Masonry gallery block and a few images.
5. Check whether the gallery renders correctly on the frontend.

If the issue still happens in that clean environment, please send me the results of that test, including the theme name, WordPress version, plugin version, and any console/PHP errors. In that case, I will treat it as a confirmed plugin issue and investigate it from the plugin side.

However, if the gallery works correctly in the clean environment, then the problem is caused by a conflict with the active theme, another plugin, or site optimization/caching settings.

@alanintertec
Thank you for the update.

That is very helpful information. So the issue was caused by the Lazy Load Media feature in the SiteGround Speed Optimizer plugin, not by the gallery data being lost in the editor.

SimpLy Gallery Block already includes lazy loading support for gallery images, so an additional lazy-load layer is usually not needed for galleries created with the plugin.

In this case, it looks like the external lazy-load/optimization feature modified the frontend output and interfered with the gallery data used by the frontend script. When that happens, the gallery script can load, but it cannot find the required gallery data and may show the “Gallery data is missing” message.

I’ll keep this case in mind and check whether anything can be improved on the plugin side to make galleries more resistant to this type of conflict.

Thanks again for confirming the cause.

Recommended fix for SiteGround Speed Optimizer / Lazy Load Media conflict:

Open the affected gallery block in the editor, then go to:

Gallery Settings → Media HTML Output → Inline HTML

This changes the fallback gallery output from <noscript> HTML to hidden inline HTML. It avoids cases where optimization plugins remove <noscript> tags and expose fallback media on the frontend.

If possible, also disable the external Lazy Load Media feature for pages using SimpLy Gallery Block, because the plugin already includes lazy loading for gallery images.