New slides not loading

Hi,

Our current Master Slider slides are working just fine, but when I go to try and add new slides in both preview and on live pages I get an endless spinning wheel, and when I go back into the slide builder the image I’ve just dropped in and saved is now showing up as a blank white slide for both the slide and the thumbnail.

Seems like other people have been having similar problems but I’ve not been able to determine a fix.

Our website is https://www.europeancabinets.com/

We’re running WordPress 4.4.2 running TwentyTwelve Child theme.

Thanks