Problem/Bug New Server Help - In Detail

Hi guys im working on an adevnture map for my son and friends, i could really use some help with the connection issues we're having.

I port forwarded on 25565 udp and tcp both in and out
I have allowed cmd, all the java.exe's through firewall and windows defender firewall
I have also tried disabling firewall

when i check canyouseeme.com 25565 ect it always says timed out.
i can connect with localhost and 127.0.0.1 but no one can make an external connection.

also when my son connects he gets the error: failed to connect to the server io.netty.channel.abstractchann...

I'm currently using forge with shaders to connect and everything runs fine, my son has tried vanilla and optifine to connect both got this error, does he require forge to connect to the server since its bukkit? first time using it.

server properties server ip is blank and online mode is enabled.

thank you for your time and i appreciate you taking the time to help.