Bad experience. Plugin has conflict with cloudflare

I had a few terrible days.
After I changed the mini CSS setting in this plugin setting and turned on the development mode of
Cloudflare in ls cache settings. Cloudflare no longer caches my website,
the number of requests and bandwidth to my origin server spiked. I reset the settings and the result is the same.
in response header homepage :
cache-control: no-cache, no-store, must-revalidate
cf-cache-status: MISS

I have added the code cache control to htaccess through this plugin.
Although the cache-control in the header has changed to public, however, cf-status still MISS.

I trying to delete all file created by Ls cache, all htaccess files, all cache, all data.
Now in response header homepage:
cache-control: max-age=0, no-cache, no-store, must-revalidate
cf-cache-status: MISS

I once again manually added the cache-control to the htaccess in pubic_html folder, but it can’t change anything. the cache-control in the header hasn’t changed to public anymore.
I am sure you have left some code in the php file and are blocking the buffer from Cloudflare.