Source game multiplayer problem

Whenever I try to connect to my buddy on GMOD or Synergy, I keep getting a message his server isn’t responding, and vice versa. Does anyone have a fix for this?

Probably because the IP to his server appears to be his local IP in the server browser. Let him use https://www.whatismyip.com/ to find out his ip, add :27015(The default source server port, change it if he have) to the end. Then you connect through console with "connect [IP]:27015.

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