"Page not found" error — HELP!!

I am having trouble with one of my galleries made through the Photo Gallery Pro plug-in.

http://www.jasminergordon.com/3d-art/

Here is one gallery that I have functioning — I am trying to create another identical gallery on another page (link below), and for some reason am receiving a “Page not found” error, and it is even causing my WordPress dashboard to act funky.

http://www.jasminergordon.com/2d-art/

I tried using the exact same settings on both, either through importing the settings or creating a brand new fresh gallery while deleting the old one. I also tried uninstalling and deleting both the gallery plug-in and the gallery pro plug-in. I had a working gallery on the “2D Art” page before, using the fixed columns gallery. I then changed the “3D Art” gallery to the “Vertical” gallery, and liked that better — so I went to change the “2D Art” page to the vertical gallery as well, and that is when it stopped working. I tried having all of the settings exactly the same as the working gallery, as well as just changing it to “Vertical” and leaving the default settings, then changing one by one — to no avail.

Any and all suggestions would be appreciated at this point. I am good enough with WordPress to know that something must be afoot in the software for this to be happening, as the conditions of the two pages are exactly the same — the only text present in the “Page” for either one of them is the shortcode for the gallery, so there are no external conflicts that I can see. The Gallery and Gallery Pro plug-ins are the only plug-ins I have instsalled on this site. I am using the “Make” WordPress child theme for “Twenty Sixteen”.

Thank you,
Justin