You need to add www (www.nocodeportal.com) seperately under Pages Custom Domains tab, just like you did for your apex (nocodeportal.com). It’ll ask to replace the current DNS Record and that’s fine.
You can think of Pages Custom Domains as having an allowlist of host headers/hostnames which are allowed, and as www isn’t configured it just fails to connect.
It is usually recommended for SEO purposes/not confusing your visitors to just do a redirect instead from www to your root/apex. There’s a guide here from Pages for that: Redirecting www to domain apex · Cloudflare Pages docs