C # Entity with id Guid does not allow me to register in database

I have modified the question as a result of your requests: first, to clarify that my database was generated using the wizard that Visual Studio has (2015 is the one I use) with the ADO.NET Entity Model (see attached image), in which I designed my entities and then generated them on the basis of data ( here I ask for an assessment of this via ).

The properties that I put in the design about the entity are these:

After the generation of the DDL, this is the SQL code of the Clock table (named by the EF as ClockSet)

CREATE TABLE [dbo].[RelojSet] (
   [Id] uniqueidentifier  NOT NULL,
   [Direccion] nvarchar(max)  NOT NULL,
   [Puerto] nvarchar(max)  NOT NULL,
   [Descripcion] nvarchar(max)  NOT NULL,
   [Activo] bit  NOT NULL,
   [LastUpdate] datetime  NULL
);
GO

The context is as follows (I have not touched anything, it is self-generated by EF):

public partial class ZKTDataBaseContainer : DbContext
{
    public ZKTDataBaseContainer()
        : base("name=ZKTDataBaseContainer")
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        throw new UnintentionalCodeFirstException();
    }

    public virtual DbSet<Reloj> RelojSet { get; set; }
    public virtual DbSet<Trabajador> TrabajadorSet { get; set; }
    public virtual DbSet<Marcaje> MarcajeSet { get; set; }
    public virtual DbSet<Settings> SettingsSet { get; set; }
}

The mapping created in the model is the one I referred to earlier:

public partial class Reloj
{
    public Reloj()
    {
        this.Marcaje = new HashSet<Marcaje>();
    }

    public System.Guid Id { get; set; }
    public string Direccion { get; set; }
    public string Puerto { get; set; }
    public string Descripcion { get; set; }
    public bool Activo { get; set; }
    public Nullable<System.DateTime> LastUpdate { get; set; }

    public virtual ICollection<Marcaje> Marcaje { get; set; }
}

In my controller, I instantiate a Clock object, and I try to persist it:

public ActionResult Create(FormCollection collection)        
    var reloj = new Reloj
    {
        Activo = collection.Get("Activo").Equals("on"),
        Descripcion = collection.Get("Descripcion"),
        Direccion = collection.Get("Direccion"),
        Puerto = collection.Get("Puerto"),
        LastUpdate = DateTime.Now,
        Id = Guid.newGuid(),   // => No funciona
        // Id = new Guid() => No Funciona
        // Id = Guid.Parse("3F2504E0-4F89-11D3-9A0C-0305E82C3301") => Tampoco
        // Id = Guid.TryParse("3F2504E0-4F89-11D3-9A0C-0305E82C3301") => Menos
    };

    try{
        using (var db = new ZKTDataBaseContainer())
        {
            db.RelojSet.Add(reloj);
            db.SaveChanges();
        }
    }catch (Exception ex){

    }
//....
}

The error generated is related to the Guid identifier of the Clock entity:

"You can not insert the NULL value in the 'Id' column, table 'ZKTDB.dbo.Settle.Rule' The column does not support NULL values INSERT error. \ r \ nThe instruction was terminated."

What am I forgetting here?