Plugin : Jetpack Slideshow stopped working

Since 3 weeks instead of my slideshows, there is a black frame with written above : “this slideshow needs javascript” (in French : “Ce diaporama nécessite javascript”). I thought it was my browser, but Siteground asks me to start a topic here : they checked for me and don’t understand what it can be (my slideshows perfectly worked since i installed the theme in august 2015).
Exemple :
Thanks in advance for your answers,
Gwendal