[Plugin: NextGEN Gallery] No Lightbox after Upgrade

Please take a look at this link. The first thumbnail (top left) was added after the update. It does not open with any “style” like lightbox etc. but rather just opens in a new window. What has happend? Can you help me and like everyone else, thank you so much for this great plugin!
Simon

https://www.ads-software.com/extend/plugins/nextgen-gallery/