@ppboomer
Check your firewall rules (or try disabling your windows firewall entirely)
Make sure your friend uses the ip you see when you visit this site: https://www.whatsmyip.org/
Make sure you forwarded port 4976 UDP
Make sure the match has been started (map loaded) before letting anyone connect
Also the config files are not gone, they are included in the archive linked in the guide (https://github.com/xerxes-at/T6ServerConfigs/archive/master.zip).