SOLVED Difficulty With Minecraft Server

This is another "cant' set up a Minecraft server" post ... I hope someone can help. The server works on my computer but it does not work on his.

Our computers are connected via Ethernet cable directly to the ASUS RT–AC86U router. His IP address for local use is 192.168.50.166. So Many Books

These are the settings for port forwarding:

Service Name: Minecraft Source IP: (blank) Port Range: 25565 Local IP: 192.168.50.166 Local Port: 25565 TCP: BOTH

If he is running Minecraft on his own computer and connects directly to 192.168.50.166 and connects. However when he enters the external IP (obtained from the "Network Map" page of the router's settings), it yields the error:

Failed to connect to the server io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection timed out: no further information

I am getting the same error in Minecraft when I attempt to connect to 192.168.50.166 from my computer.

But here's the real kicker ... Everything works if I run the server on my computer (192.168.50.48) and modify the Local IP port forward settings accordingly. I can connect to the Minecraft server using either my local IP or with the external IP.