Hello everyone,
PC user here, running WIN 10 and similar to so many others I have had multiplayer-problems with Forza Horizon 4 basically since september 28th. Only 1 playing session have I been able to join “live”, but the problem was back the session after.
And like so many others I have tried so many different solutions - suggested by Microsoft and by the community. Even though 99/100 have not worked for me, I still wish to thank everyone for their efforts, as it has lead me to get it to work now, all the time.
I am sure in the end this will be fixed so I don’t have to do ANYTHING before playing, but as it is now the solution requires me to change one service before I play. Now as I am a firm believer in giving credit to where or to whom it belongs, here goes my (finally) easy way to get it to work. I so much hope it will help others:
The first step was to understand what HAWX8901 meant with his post (#70) 4 days ago. He had to explain it a little more in a 2nd post thanks to TileHammer who asked if Hawx8901 could elaborate, which he did in post #73.
“Of course, so what I found before was that my IPV4 DNS server showed 1.1.1.1 and 1.0.0.1, after the reset it changed to just my router’s IP address. To change the IPV4 address to match the routers IP, you need to right click on your network on the bottom right of the screen and click on “open network and sharing center.” After that find “change apapter options,” click it. Right click on the network you’re currently using and select properties. Find where it says “Internet Protocol Version 4(TCP/IPV4),” click on it to highlight it. After that look under the list and click on properties. On that screen you should see DNS server on the bottom. Make sure that it is set to “Obtain DNS server address automatically” and hopefully that should enable you to play online.”
Now I am not a computer expert and therefore not that good at the internet-of-things and how it actually works, but I did manage to follow his instructions. Problem was for me though that everything looked fine at my end. So what to do? Was this another dead end. Then I got a hunch. Since there were no numbers at all representing IPV4 DNS-server I had to try and fill in those numbers myself that were mentioned in the post: 1.1.1.1 and 1.0.0.1 as they were not there.

I then checked status of XBOX networking and HELLO the server connectivity issue was GONE! I was now CONNECTED. BUT I still had a problem with NAT and TEREDO. I am so sorry about this but I can not find who posted this text that follows (EDIT IT WAS ETHERMAZE, FIRST POST ON PAGE 4!):
"As unbelievable as this may be, I fixed the issue by enabling automatic startup of the windows update service.
Open the Services window, locate the Windows Update Service, open its Properties and select Automatic as Startup Type. Apply and start the service.
Hope it helps!"
So I checked the status of the Windows Update Service and wouldn’t you believe it: IT WASN’T RUNNING. So I right-clicked it and entered the admin-version of services and RESTARTED it. It was already marked as an automatic startup (which makes me wonder if it really should be on manual but I’ll leave that up to each and everyone).
Anyhow after restarting it my XBOX networking status on my PC became as follows:

and in my XBOX-APPLICATION:

My packet loss went down from 50% to 7% and joining an ONLINE-SESSION in the game took about 10 SECONDS!
TO SUMMARIZE THE TWO SIMPLE STEPS THAT FINALLY FIXED IT FOR ME:
1. MANUALLY ENTER DNS-SERVER INFO WITH 1.1.1.1 AND 1.0.0.1 INSTEAD OF HAVING IT ON AUTOMATIC
2. RE-START THE WINDOWS UPDATE SERVER (MINE SEEMS TO SHUT DOWN EVERY RE-BOOT)
START THE GAME
HOPE THIS HELPS!
EDIT: I have since posting this noticed that the Internet Protocol Version 4 Properties change settings back to “Obtain DNS server address automatcially”. I noticed it when the game suiddenly wanted to sync my game with the cloud. All I had done was restart the game as I had changed the graphic settings so I suspect that is what caused this. The game couldn’t sync and alerted me that internet connection instability was evident. I alt-tabbed and re-entered 1.1.1.1 as primiary and 1.0.0.1 as backup, got back into the game, and internet connection was now stabilized. So heads up regarding that: I have to re-start windows update service after a computer-reboot and manually re-enter the DNS-info after a Forza 4 re-start.
Sincerely,
awaken3D / Fredrik