Can you check whether it was cached on Cloudflare or not?
Cloudflare does not cache the resource when:
The Cache-Control header is set to private, no-store, no-cache, or max-age=0.
The Set-Cookie header exists.
Cloudflare only caches resources within the Cloudflare data center that serve the request. Cloudflare does not cache off-site or third-party resources, such as Facebook or Flickr, or content hosted on unproxied (grey-clouded) DNS records.
We highly encourage you to read more about Cloudflare’s Default Cache Behavior · Cloudflare Cache (CDN) Default Cache Behavior) to understand Cloudflare Cache Behavior.
You can create a Cache Rules with Edge Cache TTL. Please kindly find the instruction at Create Edge Cache TTL page rules · Cloudflare Cache (CDN) Cache Rules settings).
You can also follow the instructions Optimize site speed Speed).