521 = Origin server down; I.e. the port is not open and/or the IP address is incorrect all together.
522 = Origin server time out; I.e. the port might be open but no content is being sent back.
If you’re seeing 521, then Cloudflare cannot establish a connection to port 80/443 on your IP address in the A record. Bearing in mind that in order for someone from outside of your LAN (i.e CloudFlare) to have access to your services, they must be able to reach the service, so this value should be your external IP address, not an internal address. Once you have your external address keyed into the record, have someone else not in your home try to access that IP/port combination and see what happens. If they cannot access, then port forwarding is not setup or your ISP is blocking, or you’re behind some CGNAT. If they can access, then something else is at play (origin IP filtering comes to mind).