SOLVED Difficulty With Minecraft Server

This is another "cant' set up a Minecraft server" post ... Hoping someone will be able to help. The short version is that the server works on my computer, but not on his.

Both of our computers are wired directly to the ASUS the RT-AC86U router with an ethernet cable. MINECRAFT is 192.168.50.166.

The port forwarding settings are:

Service Name: Minecraft Source IP (blank). Port Range: 2565 Local IP: 192.168.50.166 Port: 25565 TCP: BOTH

If he is running Minecraft on his own computer and directly connects to 192.168.50.166 and connects. However when he enters the external IP (obtained via the "Network Map" page of the router's settings) this will result in the following error message:

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

When I try to connect from my computer to 192.168.50.166 I get the exact same error message from Minecraft.

But here's the real kicker ... If I run the server on MY computer (192.168.50.48) and alter the Local IP port forward settings according to my preferences, everything works. I can connect to the Minecraft server via either my local IP or an external IP.