Need some help with "Not available outside your network"

I just moved my Plex server from one computer to another, and uninstalled it from the old PC. My old Plex was connecting just fine, but the new Plex is having trouble connecting outside the network. When I first set up Plex about 6 years ago, it took me a while, but I eventually figured it out. It’s been so long, I can’t remember what I did the first time to get it to work.

I’ve already been through all the troubleshooting. I even made a static IP, which I know I didn’t have to do with my old Plex.

It is an older router (Actiontec MI424-WR). I don’t think it has NAT-PMP or UPnP. I don’t have double NAT. I have no idea what Jumbo Frames are, but I don’t have the symptoms the troubleshooter is talking about. I manually assigned a static IP, like I mentioned before. Here’s how I have the port forwarding set up:

Here’s the port forwarding part of Plex:

Another thread mentioned Windows Firewall, but I checked that and it says it’s allowing Plex through the firewall.

I’m at a bit of a loss. Any other ideas? Do I have port forwarding screwed up? Did I mess up the static IP?

Delete all of those port forward entries in your router, then reboot the router. Create a single new port forward entry that points to the Plex server machine IP, for port 46777, protocol TCP. In the Plex server settings, enter 46777 in the public port box, then click retry.

It turns out, rebooting the computer fixed it. Why oh why didn’t I try the obvious thing first?