Just installed win version 1809 tried everything else open ports on router still no luck, I’m from Croatia
What to do???
Same here, installing every single windows update hoping for the fix of this stupid problem. Every time i open windows i input the comand lines mentioned on the 1st page of the post, that usually makes the Teredo server open for me, but now, even with the server open the game just refuses to connect me online.
I seriously left this game abandoned like a month ago, just because of this stupid connection problems… So sad, that will make me think twice before buy everything that is associated with Microsoft.
+1
i have the same problem, although my NAT is moderate
Fixed it. For me… But i really hope this does help you too guys.
First thing to do, is: Check if your Router filters out Teredo:
On my german Fritz!Box (Cant change language, sorry) i had to uncheck: “Teredo-Filter active”, It reads further: “This filter blocks teredo-packets. Teredo is a tunnel protocol. Devices in your home network can build a own ipv6 connection and bypass your routers firewall. Teredo isn’t required normally, if your router does support a native ipv6 connection in your home network. Deactivate the teredo filter only, if a device in your network does require teredo and it it is okay for you if some of your devices can bypass the router firewall via ipv6”
Alright. Second thing i did was checking if teredo is running correctily on my pc. Spoiler: It wasn’t. So:
- Open CMD (Command Prompt) as admin
- type in netsh interface Teredo show state
Check what it says. If something is disabled or not ok, type:
- netsh interface Teredo set state type=default
If above command didn’t work, this was the case also for me, try:
- netsh int teredo set state natawareclient
Finally this worked. Xbox App is connecting fine and Horizon online mode working.
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Thank you sir!/Dank dir!
The last steps described by you worked for me, it was somehow suddently disabled. now its runnig properly 
Grüße aus DE^^
today i was with support for 2 hours and we kept going through steps well while doing so i found that the save data is messed up i tried my account on two Xboxs and one pc on different networks all the same issue i then tried a alt account and it worked no problem no errors so for the error 0x00000000 seems to be save data issue not sure but the support guy submitted it to the system engineers but im not sure if that’ll fix the issue
Okay [Mod Edit - Abbreviated profanity, profanity and profanity that is disguised but still alludes to the words are not permitted - D]
My NAT type is open and server connected and still can/t play online!!
Same here , for this game and for Forza Motorsport 7 I can’t play online because servers are not available (I have NAT open and tried everything)
Same problem with me.
Same for me, IPSEC: 0x00000000
Hey I’m not sure what caused it but hold the power button on the Xbox till it turns off then unplug the power cord for ten to fifteen seconds plug it back in and it should reset the Xbox I was able to get right on forza and get on horizon life with no issues hope this helps
Problem is back ,online not working .
I just ended up fixing my game same error since October 2018.Mines said ipsec 0x00000000 .anybody still having the issue post back so I won’t waist my time.
How did you fixed it?
me to
On the part of technical support also encountered a complete disregard. Online does not work from 14 December. Especially in order to play online FH4 made a new account, but after two weeks I was faced with the same problem IPSEC. More bad technical support, I have never met.
i have the same problem as alot of you all on here, this happened initially on xbox one so i created a new account and it works 
which is no good to me as everything i have is on my old account, i downloaded fh4 to my pc and im getting the same problem on that too and ive done all the ipsec and nat stuff etc, but how can it be a network error on my end if i can get online with a new account?? anyone got any ideas how that could be?? thanks
I would like to add chat results with Xbox technical support. I talked with them for about two hours. I cleared the console cache, deleted the save only from the console, deleted the save completely (from the console and the server), changed the DNS, completely deleted my account from the console, reinstalled the game, reset the console to the factory settings with full removal. None of these manipulations helped me get online back into the game. Those. The problem is exactly in my player tag and the information stored on your server. The most interesting thing is that a week after I created my second account, it also stopped working online, this time for no reason. On this account, I conducted all the experiments. Xbox Live on my console works fully. Keep in mind that if you have an IPSEС error on Xbox One, all these manipulations are a waste of time.
Unbelievably what a company like microsoft can afford, do not know whether to laugh or breathe …