Hi,
I use on one of my websites online banner ADs. the Cloudflare caching prevent that the banner change if the side is new loaded. Page rules not work because the source is an external URL.
Cloudflare doesn’t cache external resources. It may be caching the resource on your site that’s calling banners, so your cached resource keeps calling the same banner. If you can figure out which resource that is, you can create a Page Rule to Bypass cache for that resource.