Wondering if anyone can explain what’s going on so here we go, I can access the hopper menu and join into a lobby with no issue but as soon as the vote for a new track countdown ends and the countdown to begin the event begins I get two warnings about low bandwidth and high latency then it kicks me from the lobby and says multiplayer is not available and to try again later. I have had this issue since day one but really didn’t care because I don’t like playing online. But with this forzathon I have to go online to get the reward. Any help at all would be appreciated because my aggravation levels are through the roof at this point.
No reply’s or advice, no knowledgeable input from anyone? Fantastic.
Did you uninstall everything and redownload? Seems like a strange issue. Does this happen at all with any other games? You mentioned you don’t like playing online much. Might be a connection issue with the system? Just tossing out some things here.
All my other games work fine and I did reinstall the game once recently to see if that would fix it, and it didn’t help. I don’t like to play the Motorsport games online because of wreckers and such, but I play all my other games online and have no problems, except for this game. I’ve had issues with some pc games online servers just not working with my internet before, maybe this is the same situation? But those games were small indie type games so idk.
Sounds like NAT restriction.
Check if there are connection errors or NAT restrictions with xbox live.
Start, options, gaming, xbox network on PC otherwise network settings on xbox.
And please Google. The web is full of solutions regarding Xbox and Microsoft store apps (games). 
Use a network cable instead of wifi.
I am using a cable, and my nat is normal and all my other games work fine. It’s just this game that is not working. I’m just going to have to deal with the fact that I’m not going to get this forzathon car and any other ones requiring online play.
Have same issue.
Changed teredo settings, changed DNS, did reset evrything, did winsock reset, xbox app says evrything is fine, evry other game works flawless (including forza horizon 3), i am wired, i check firewall, tried without firewall…
As a last try i decided to reset the Forza 7 app. Dont do that. I now cannot get past synchronizing data, so i am effectively unable to reach my saved game.
after ages I am finally able to play online again.
as said in previous replies to your question, in my personal case was a NAT issue.
everything looked normal and I did not have any issue with other devices/applications… but still forza motorsport games did not work (I wasted some money on xbox live gold subscription, by the way.
I almost gave up, but in the end I found online the solution for my SPECIFIC modem, for my SPECIFIC provider, for the SPECIFIC country I live in, for the xbox one SPECIFIC needs.
I followed the instructions and… magic happened! NAT fully open.
by the way, in my case it was not “istantaneous”; after changing all the settings as per the online instructions, it took several minutes for the xbox to recognize the changes on the network connection.
maybe I was lucky to find exactly my setup, but given the amount of information on the web, it could be worth the effort (if you have not yet tried… of course!)
good luck!
musmo
well, my nat arleady is open and it still doesnt work, but forza horizon 3 does 