How to setup a normally offline Plex server

Hey guys,

So I had this working in the past but switched computers and am starting over from scratch and can’t get it to work.

I work on a boat and internet connection is obviously not reliable. I’ve got plex setup on a Windows machine (previously Mac) with an offline router so anyone on the boat can access the Plex on their computer and everyone’s happy. Like I said, this used to work. Worked for the last couple years but it’s not now.

When I broadcast a WiFi from my phone everything works. When on the offline router and trying to access Plex from another computer I get a “Plex not reachable” warning.

Things I’ve seen in forum posts and tried to address:
Secured connections: preferred (tried disabled as well)
Local network Discovery is enabled
I’ve added my whole netmask as well as my test computers specific IP address.
For giggles and kicks I even tried a year old version of Plex and still nothing.

So please someone tell me what I’m missing