Header borders

https://kriesi.at/support/topic/full-width-image-divider-above-the-header/ this worked fine but it stopped working after (probably an update) I have the follwing code is the custom css which worked fine before

#header {
border: 10px solid transparent;
-webkit-border-image: url(http://www.flex-co.nl/wp-content/uploads/2016/09/lijn-kleur.jpg) 30 round;
border-image: url(http://www.flex-co.nl/wp-content/uploads/2016/09/lijn-kleur.jpg) 30 round;
border-right: none; border-left: none;
}

#header { border-image-repeat: stretch; }

Any idea why this stopped working on http://www.flex-co.nl ? it seems that the image is just not show, the space is still there. The image is still live / on the server