Website is down though the server is UP

My 2 sites are hosted on Contabo and serving through Cloudflare. Both of them are down since 12 hours. I pinged my server IP and found it is online. I am using AAPanel. I restarted both AAPanel and Server but still no luck. What could be the issue here?

Are you able to connect directly to, rather than just ping, your origin server? (Or you can pause Cloudflare to try and see what the origin server is returning).

Check for SSL certificate expiry on the origin.