Plugin only works in "Live Preview"

I wanted to check here before I attempt a rollback. I have a custom plugin where a member can upload images. They are viewed in a custom gallery then individual images are shown in a custom post type. Everything still works except the gallery page. It shows thumbnails in rows and columns and paginates, but while the page url changes, the page itself stays on page one.

I have deactivated all plugins and tried default themes. The weird thing is, it works perfectly in a “Live Preview” window for any theme, but not in an activated theme.

Do I need to rollback? Or is there a simpler solution.

I’m very new to WordPress…