The problem stems from having a different website and WordPress URL. If you go to Settings > General you’ll see that your Site URL is http://www.lavit-apnee-club.fr and your WordPress URL is http://188.141.173.99/LAC/. Hosts don’t allow assets to be loaded across domains in this manner. I’ve done a quick check and you should be able to set your WordPress and Site URL’s to the same address without breaking anything: