XF 1.2 Clicking on attachment thumbnail

[motowebmaster]

One of my users said that when he clicks on an image/thumbnail, from an uploaded image attachment, the view isn't same as it is for me. He sees the picture on a new tab in his browser.

What causes this behavior? I'm seeing a lightbox for the same but this user isn't.

 

[Jeremy]

Light box is disabled once you drop below a certain width (so mobile users can actually see the content)