Customify image lightbox behavior follows WordPress core, so an Image block opens in a lightbox only when you enable it.
This applies to the WordPress core Image block inside pages and posts. It is separate from Customify layout controls such as Customify Page Settings or the background image guide.
Turn on the Image block lightbox
- Edit the page or post that contains the image.
- Click the Image block you want to open in a lightbox.
- Open the block toolbar or settings sidebar.
- Enable Enlarge on click or Expand on Click, depending on the WordPress version shown on your site.
- Click Update or Publish. Clicking that image on the front end now opens it in the WordPress lightbox.

Why it changed in Customify 0.4.21
Customify 0.4.21 restored the WordPress default: image lightbox is opt-in per Image block. A short-lived update had forced the lightbox on, but current Customify versions let each block decide.
If the page layout still looks wrong after enabling the image lightbox, check full width page settings or contact support with the page URL and browser details.