Hi,
In HikaShop 6.5.1, we've added a new option "Generate AVIF images" to HikaShop's configuration page in order to generate AVIF images for the products and categories images. These will improve speed and SEO on your website.
Since there is no downside to having this setting activated, we decided to turn it on by default.
However, on your website the WAF security system is blocking access to avif files. So even though HikaShop is able to generate the files, and add the HTML, the browser is blocked from downloading them, which is why you get this problem.
We didn't anticipate this would happen.
Turning off that "Generate AVIF images" setting fixes the problem on your website.
Ideally, it would be great if your WAF could allow for avif images since it's becoming a standard format for web images.
That would allow you to turn on this setting.
For now, we've made a patch to keep that setting turned off by default for others, following your feedback.