Images Popups Not Working

I am writing to report an issue that has suddenly stopped working on my site. Specifically, when I click on an image, it no longer displays a popup on any posts. I have attempted to troubleshoot the issue by disabling the Cache plugin, but the problem persists.

I kindly request that you investigate the matter and provide a solution. If there is anything I can do to assist with the resolution, please let me know.

The page I need help with: [log in to see the link]