I CANT CONNECT TO MY FRIENDS GAME! (Connection failed after 6 retries)

So I tried joining my friend on Gmod, and when the loading screen came on when I hit join game by clicking on the arrow for his steam, it gets stuck on connecting to server… then it shows a message on the G and it says: “Connection failed after 6 retries.” The thing is though, my other friend can join him, but not me, someone please help!

THINGS I HAVE TRIED DOING ALREADY!
-Disabling all of my firewall
-Reinstalling Garry’s Mod, I got it to work again ONCE
-Factory Resetting Garry’s Mod, then verifying the game cache, this worked TWICE
-I tried putting p2p_enabled 1 in the developed console but it says error or something when I try to connect to them
-I tried troubleshooting my network
-I tried turning off firewall just for Garry’s Mod (Only let me turn off one, I choose public)
-I tried checking the Valve Server Browser and servers were there for the games I had