The problem with CG-NAT addressing is that it does not support port forwarding. Also, the public IP address used when you cruise the Internet is shared with others.
Plex needs a unique IP address, one not shared with others, for remote access to function.
When the ISP assigns the address, you can use either UPnP (automatic port forwarding) or manual port forwarding to enable remote access.
The public IP address will be registered at plex.tv. Then, when you, or someone to which you grant access, wants to stream remotely from your server, the client (app) checks with plex.tv, which tells them the public IP address of your server. Then they can stream remotely.
There’s some more handshaking regarding logins, which libraries, are shared, etc., but that is the basics.
Getting back to configuration…
You’ll configure remote access in Settings → Remote Access. If you use manual port forwarding you will also need to configure a port forwarding statement in the eero router (it tells the router to forward the packets to your Plex server).
The basics are covered in Plex Docs → Remote Access & Granting Library Access.
Another helpful document is The Basics of Remote Access Troubleshooting .
