cannot connect other players error

i can succesfuly logged to online but my friend had a cannot connect to other players error how can i solve it i couldnt find any solutions can you help me abaou this error

Also having similar problems too! I'm getting the grey phone icon everytime, and connection test passes with no issues. Game was working two weeks ago with the same peers without issues. We've tried excepting the game from the firewall, disabling the firewall, reinstalling the game and rehooking with no luck! Please help us!!!