Open the /Data/Models/ApplicationUser.cs file and add the following Lazy-Load property to the end:

[...]

#region Lazy-Load Properties
/// <summary>
/// A list of all the quiz created by this users.
/// </summary>
public virtual List<Quiz> Quizzes { get; set; }

/// <summary>
/// A list of all the refresh tokens issued for this users.
/// </summary>
public virtual List<Token> Tokens { get; set; }
#endregion

[...]