If you play/will play on the PC, and you have played on somebody else’s XB1 using your MS account, you might find this useful.
The fist time I started KI on PC it told me I have a save from somewhere else and it gave me the choice to either go back to the XB1 and sync from there or discard that file. I chose to discard and start a new file, and the game worked fine that time.
The next time I tried it had issues syncing my data from the cloud. It failed everytime at 14%, 16% or 22%. Keep in mind, I had NO TEREDO ISSUES, I could connect to XB live and to online lobbies. Somehow my save data had become corrupted. Sometimes it would just check for updates forever.
What I had to do is use my brother’s XB1 to start KI with my account again, then it asked me what data do I want to sync, the cloud’s or the XB1’s I was using. Whenever I tried to sync from the cloud if failed just like in W10. When I sync from the XB1 it worked. I then deleted my account from the XB1 and went to check KI W10. It synced fine afterwards.
I know I could have do the XB1 part first to avoid issues, but if KI offers the choice to “discard and start a new file under W10” it should work. I don’t know if it is an isolated issue, or not, but here is how you can fix that if it happens to you.