NAT loopback C3000z possible

I'm sorry if this has been asked before, I promise I did search.

A relative has CL fiber and the infamous c3000Z Modem/router. Setting up a web server, it can be accessed remotely fine but on LAN the nslookup fails and connections timeout attempting to resolve mydomain.ltd Most have networking device I've used in the past have NAT loopback or some sort fo redirect. I've tried everything from the DNS host mappings to all the application and port forward rules, to even moving the hosting server outside to a DMZ. Same results locally.

Network setup is C3000Z to a dummy 8 port switch to said web server. External access isn't an issue, just when on the LAN. There is a wireless AP R8500 that if possible I could circumvent the C3000Z altogether. (It used to run in bridge mode and the R8500 handled all the routing so I know the issue is with the C3000Z. I've read articles regarding telnet'ing into the modem and enabling nat loopback but that was for older c2100 dsl modems. Any advice would greatly be appreciated and feel free to ask for any additional information IF any of this was unclear. Thanks.