Dear @axeldemarteau
To be sure before progressing :)
Wordpress, Lay Theme & Laytheme's Addons are all up to date ? Any Custom CSS or JS that may interfere is temporarily removed. Any third-party plugins de-activated to see if this resolves the issue. If using a WordPress Cache plugin, disable it or clear your cache. License key not activated - (in website blank situations or button not available) If your WordPress Dashboard shows a warning "PHP Update required"please update your PHP version in your webhost control panel. Additionally please take a look at https://laytheme.com/troubleshooting.html for known problems.
Hope this helps & best wishes :)
Richard