Hello I have a similar problem, when I attach a gallery to a page I see only one thumbnail and that’s it.
So I searched a bit and read this thread, which is like the problem mentioned by Brian:
https://www.ads-software.com/support/topic/gallery-url-definition-problem?replies=4
HOWEVER! My problem is a bit more complicated. Because when I remove the added /wp/ I do get indeed to see the image-browser, but no pictures! Although it says: picture 1 of 15. And I get to click back and next… but no image appears.
To add to my freaking-outness at the moment, this all happens to the website of a friend I am making right now… I tested it this afternoon on my own website and it was working fine…. even WITH the /wp/ so there it didn’t seem to matter at all.
I deactivated all the plugins on my friends website, went to Twenty-Twelve theme… and it didn’t help anything… back to my own website, it works fine…
Copied the child theme of my own website to my friends website, nada…
we’re with the same provider, albeit on different servers, so I don’t think that should be the problem. Everything is updated… reinstalled, checked and double checked… it works on my site and not on his.
Please help, it’s driving me nuts…