Unfortunately I haven’t really used VirutalBox myself much, beyond the prototype to show that it worked when I wrote the VM instructions. I know that the key was the two steps (misnumbered as 1&2) after the IP config image in the article here, where you set up the network access and port forwarding. If you double check those steps and ruled out firewall issue, I’m afraid I’m stumped.
You could also try the ansible installer by @Mudpuppy. It’s not officially supported (I don’t know anything about ansible), but it might be worth a try if the other way isn’t working.