I've been trying for the lase week to use GitHub from NB from a Windows 10 machine. Very little success. The problem is the first Push step (Next) seems to time out will trying to connect, giving a Fail to Connect error. If Next is clicked again it often seems to connect... no more "failed to connect" message. However, the Finish step fails with a "cannot open git receive pack" message. On rare occasion, both steps succeed.
I am aware that there have been reported Windows 10 page load load time issues from the beginning, so am suspicious. But I report this thinking I am probably not the only person with the problem. For now, NB GitHub is useless. Too bad.