That's not related to Cloudflare though. That website/subdomain is unproxied, your origin is serving the expired cert to visitors. Your universal cert doesn't matter as it's not going through Cloudflare, just need to get your origin to renew the certificate
I am using a host provider they use jexactyl (mini servers) with reverse proxy I am using node.js as a program language idk much on what they use for the proxy.
they give the options to use the SSL or not I turn off give SSL and I even tried generating a new one using another provider instead and it didn't work.
"Cloudflare used its own ssl" is a dangerous statement. While it's true you can have a setup like that User -> Https -> Cloudflare -> http -> backend, it's very insecure and not recommended