WebP Support not working

Hi,

i created WebP Versions of my images and installed cache enabler on a multisite. I checked the field to deliver WebP Versions of images to browsers. When i now check loading my site in chrome developer tools, no .webp images are loaded. Still the PNGs and JPGs. On my server in the /cache folder, there the webp-Versions of the cached pages exist and in source code it is shown, that the site is delivered by cache enabler. What could be wrong?