How to I connect both my app and server to the same subnet?

I’m new to this and I’m not much of a networking wiz, so play nice please.

Plex worked fine for a while, but ever since a couple months ago I have been getting the message saying that it is unable to connect to my macbook. It goes on saying “We tried to connect to: [a string of numbers that I assume to be my IP?]… Your Plex Media server and device are on different subnets.” I’ve tried opening my “Open Settings” to type in the IP address that I get on my Mac, but that doesn’t work. I’ve also tried plugging my ps4 into a lan line to see if anything would change and there is no change at all.

Any help is appreciated. Thanks in advance.

Could you please further elaborate on your network setup? To what is the server and client connected?

Both my ps4 and macbook are connected to my in home wifi. Any settings for my modem have stayed the same since I got it. I use centurylink (if that helps) with a standard modem.

Is this a combined modem-router with included WIFI or do you have two separate boxes? If it is the first, a combined such, perhaps calling your ISP asking for help to factory reset it. A normal home network should never have to involve different subnets. It might be a misconfiguration or such that makes your router act as a switch only.

It could be also either a DNS failure with *.plex.direct or a DNS rebinding issue.

Does it work if you disable ‘Secure Connections’, followed by a server restart?
Settings - Server - Network

True, got blinded by the error message. Thanks, Otto.