[Plugin: NextGen] doesn't load the image after clicking the thumb

Hi,
please take a look at my demosite “Galerie”:
https://makeupstudio.academia-canis.at

After clicking the thumbnail, I get an empty page instead of the large image.

When I look at the demo from NextGen itself, the URL doesn’t change when the lightbox with the image opens.
On my site, the URL changes to the URL of the single image, but with that “/#!/” inside. When I remove this “/#!/” I see the image without a lightbox.

The support of the theme (comercial, elegantthemes.com), I was told the “/#!/” cannot be removed.

Thanks for your help,
Andrea