Issues resolved

Felt this was a good place to post the solution that support found, for me. Had recently installed Mingle, a forum plug-in, and apparently some code in it caused my photo galleries to go down entirely on computers, nothing but a white screen. Yet the galleries were still visible on mobile devices, but without lightbox functionality…
Deactivated my forum plugin and, voila, everything back to normal.

Hope this can help anyone else with similar issues.