If your getting a 404 not found error when requesting .webp files when using Azure App Services and your sure the files exist you likely need to add the WebP mime type.
You can do this by adding a Web.Config file (if one doesn’t already exist) to your wwwroot folder which contains a mapping from the webp extension to the image/webp mime type. For example..
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<staticContent>
<mimeMap fileExtension="webp" mimeType="image/webp" />
</staticContent>
</system.webServer>
</configuration>