Hi there,
Those are Wordpress notices which usually appears on top of the page, and it’s moved below and affect the visual view of the slider. It’s not because of license or activation.
And I think, the issue itself is the content
<h2 style="font-family: "open sans"; font-size: 70px; letter-spacing: 0; color: #ffffff; border-bottom: 4px solid #ffffff; line-height: 68px;">Nous créons <br>l’événement</h2>
I duplicated your slider and changed it’s content to this
<h3 style="font-family: "open sans"; font-size: 70px; letter-spacing: 0; color: #ffffff; border-bottom: 4px solid #ffffff; line-height: 68px;">Nous créons <br>l’événement</h3>
And there is no issue anymore. Something is merging the h1 and h2 together including the notices. I can’t reproduce this on my installation. It could due to custom javascript, or from a 3rd party plugin’s javascript.
You could try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Let us know how it goes!