Hmm. Well https://dnschecker.org/#A/forum.procedural.audio shows that the name resolves in a bunch of places, so maybe it’s a propagation issue. When I have 1.1.1.1 or 8.8.8.8 look it up, I get no response. NS-337.AWSDNS-42.COM does return it though, so you might just need to wait a while.
But discourse-setup will try to look up the address and see if it can connect to itself. If that is failing it’s typically either and DNS issue or that ports are not open.