So I've been having this issue since I first started to play ARR earlier this year. Basically my launcher won't remember my user id or password. I've read on other topics that this can be cause by internet options being set to clear history automatically. However I've checked both my main options in the control panel, plus my Fire Fox options.

Both are set to keep history until I manually delete. So I'm not sure if there's a spefic Windows 10 issue with the launcher that I haven't found yet.