Slideshow is no longer working

Hello,

I have a problem with the plugin. Today, I tried to insert a slideshow into a post, but I’m not able to select a gallery. There’s only a loading cycle where I can choose which gallery I want to use. If I use the shortcode, there’s only a loading cycle on the page. Logging out does not help. What can I do?

Greetings

https://ww.wp.xz.cn/plugins/nextcellent-gallery-nextgen-legacy/