ERR_NAME_NOT_RESOLVED?

Why does the website fail to load when connected to Cloudflare?
Google Chrome displays: ERR_NAME_NOT_RESOLVED, while Firefox displays: PR_CONNECT_RESET_ERROR.
The website loads normally without using Cloudflare’s proxy. SSL, whether set to Flexible or Full, doesn’t work.
It seems to be related to Cloudflare’s proxy.

What is the site?

I tested with different networks again, and the broadband network will show an ERR_NAME_NOT_RESOLVED error. It works fine with the 4G network on my phone. Is there a solution to this situation?