How is VirtualBox networking configured for you guest? NetworkManager controls the network these days and there are more steps required to configure a static IP address then posted in the guide. I hope you did not use the exact values shown in the guide since they may not match your actual environment.
So you could have an address conflict, port conflict or selinux preventing apache from listening on the desired port. What happens if you change 3221 back to 80?
https://wiki.apache.org/httpd/CouldNotBindToAddress