No insert options after click on page icon

Hi,
I have just installed Next Gen
I checked the options for theme compatability – that was okay

I created a gallery

I went to the page to add the gallery – clicked the icon in top formating bar on the page

and all that popped up was a big white box with a x in the corner to close it – no options, no text visible in the box

Any ideas?
Cheers
Amanda

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