MLAPI - Host in editor not working

I am making a game with MLAPI.

On my pc
I can host in build, join in editor - works
I can host in editor, join in build - works

I can host in build, brother joins - works
I can host in editor, brother joins - DOES NOT WORK
My bro can host in editor or build and I can join to either.

Bro does not live in same house.
The connection port is my external IP.
My firewall allows both Build and Unity version through it.
I have port forwarding on my router to my local address.

Any reason why it does not work for me in editor but works in build?