ASP.NET Core Identity Cant create user

Hello everybody,

I install Visual studio Community 2017, create new project, create SQL Database in Microsoft Server, want to create admin role and asign user to that role.

Making everything by this gide: https://code.msdn.microsoft.com/ASPNET-MVC-5-Security-And-44cbdb97

Database is created, Admin Role is created, but create user return false:

 var chkUser = UserManager.Create(user, userPWD);  

chkUser.Succeeded = false

Do not understand why?