Image-Title or Image-Title is not shown in Gallery

Same problem here ??
Is there an easy way to show the title/alt-tag in colorbox?

WordPress used to add the title attribute in galleries, which powers the title showing in the overlay – now, unfortunately, it doesn’t add it automatically.

See this post by Tommy78 for a simple solution in your functions.php file: https://www.ads-software.com/support/topic/add-the-title-of-an-image-to-the-image-link-in-gallery#post-4840514

Hope that helps!
Opal