Media Viewer is unable to load image previews. Thumbnails display on published pages, but after clicking on image to open in Media Viewer, an error message occurs.
Private wiki is mlharchive.miraheze.org
Example is image on https://mlharchive.miraheze.org/wiki/MLH_Family_Archive_Main_Page.
Had same issue with pastport.org last month and was pleased to see it fixed quickly.