Not sure what to suggest - the instructions for a standard install should always be successful. Somewhere, something has gone wrong, and you didn’t see it, or you didn’t share it. It’s very difficult to help when we can’t see.
I notice you changed the wget command - you did not paste the exact command. So I don’t think we can learn anything from that. Perhaps you should try again.
You did not answer the question about the DNS. You should try to ping your fully qualified domain name
ping -c2 your.full.domain.name.com
but of course using your own domain name. You should check to see if the IP address that’s reported is exactly the same as the IP address of your server.
It would be helpful to share the full session output - of course, remove any private details first.