Make sure you’ve followed his advice to.the.letter.
403 Forbidden suggests you have not set up permissions on the server correctly.
You wouldn’t get that unless you weren’t at least connecting to the server, so I don’t think the A record is the issue.
If you have questions about Canapin’s guide, I suggest you post on that Topic, not here, as that may be helpful to others how may have this kind of issue in the future.