When I try to log in xbox live, I can't.

I've been trying to log in Minecraft windows 10 Beta lots of days and I still can't. In the step that you have to write a gamertag, when I click: next step its written: You can't log in this moment in xbox live, try again later. Minutes later, I try it again and its written the same. And always when I try it, it reapeats again, again, and again... And I never can log in.

Sorry if there are some mistakes in the text.