Linux noob with dedicated server also hosting wordpress (and apache) Login server unreachable

OS Name/Version: Ubuntu 20.04

Product Name/Version: (Always use the full version number - not ‘Latest’) AMP Triton v2.3.2.4

Problem Description:

I have a Dedi Server which I am already hosting a WP Multisite on and am trying to add a Minecraft (Forge 1.18.x) and Project Zomboid (41.66) through AMP.

When I try to manage either server I am told the server(s) are unreachable. Have followed advice on various answers, alternating between, an actual domain name, the ip of the dedi server.

I have also tried adding various bits and pieces through apt, many of which I don’t fully understand and may well be doing more damage than good.

Hosting the website(s) elsewhere isn’t really an option. I can install Docker (probably) if that will alleviate issues.

I’ve been a Windows user for 30 years and a Linux user for about a week so i’m treading water at best.