I have tried to play KI on Windows 10 but when I try to it tells me “Failed to reach matchmaking servers” I even undownloaded the redowloaded the game and still no luck. I was told to check Terendo but all that it says that it is obtained
If you have a routing program such as Hamachi on your computer, uninstall it.
I’m having a similar problem
Me as well. I have tried everything anyone has suggested to try to fix it, but as of yet, I still can not connect. Teredo is obtained, but it won’t reach matchmaking servers.
If you have a apple airport router, check out my thread on the fix.
I have deleted Himatchi and I was able to play but when I logged and came back I tried looking for a fight but the game now closes when searching.
I solved this way. I found it on the xbox forums.
If you have multiple network adapters (Virtual and/or Physical), you should check if any of the others are considered active but do not provide an internet connection and disable them if they aren’t currently needed. Ideally disable any adapter that you do not need enabled at the time to ensure it uses the proper one.
On Windows 10 you can find this from “Settings” -> “Network & Internet” -> “Wi-Fi” or “Ethernet” (You can also get here by clicking “Network Settings” on the pop-up from the Network icon on the taskbar.)
Once there, scroll down, if necessary, to the “Related Settings” section and click “Change adapter options.”
Here you can enable and disable network adapters. Remember that if you disable your Wireless or LAN adapter and later want to switch to using it, you’ll need to go back and re-enable it.
That is what was causing my issue with the Xbox App not obtaining a Teredo address.
I have a couple different virtual adapters which are sometimes active but do not provide an internet connection and for whatever reason the Xbox App decides to try and use them instead of the active internet connection that it uses to get the friends list and everything else.
problem is fixed by deleting or disabling virtual networks like windows tap v9 network driver , or hamachi driver
Oddly enough, this was my issue to connecting to the servers! Thank you @BloodRiviera83 for the suggestion 
Same issue here, I can’t even access the online shop, can you???
I’m happy to have been of help. More online players, more fun.
I was able to buy stuff on the store using the Windows 10 version when I deleted Himatchi but sometimes when I search for a match the game crashes
I solved my issue (I had teredo working). This is what I did:
1 - uninstall the game
2- enable windows update (mine was disabled): Windows Key + R -> type services.msc, find windows update, enable it
3- Windows Firewall on
4- Download the game again
5- Enable IPV6 in your internet adaptor properties
I had this problem and I tried almost every solution with no luck, I had to format my pc lol and after that I was able to play witouth problems