ASP.NET Identity Remember Me

I have built an application targeted at mobile devices. I would like to be able to check the "remember me" option when logging in, and then be automatically authenticated from that point on, whenever I visit the site (app) or click on a link in an SMS that directs my browser to an authenticated controller action.

Unfortunately, it seems that I must have something incorrectly set somewhere, as I am required to login almost every time I visit the site, even though I have selected "remember me".

In my Startup.Auth.cs file, I have the following in ConfigureAuth:

            app.CreatePerOwinContext(ApplicationDbContext.Create);
            app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
            app.CreatePerOwinContext<ApplicationRoleManager>(ApplicationRoleManager.Create);
            app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);

            // Enable the application to use a cookie to store information for the signed in user
            // and to use a cookie to temporarily store information about a user logging in with a third party login provider
            // Configure the sign in cookie
            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                LoginPath = new PathString("/Account/Login"),
                Provider = new CookieAuthenticationProvider
                {
                    // Enables the application to validate the security stamp when the user logs in.
                    // This is a security feature which is used when you change a password or add an external login to your account.  
                    OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager, ApplicationUser>(
                        validateInterval: TimeSpan.FromMinutes(30),
                        regenerateIdentity: (manager, user) => user.GenerateUserIdentityAsync(manager))
                },
                CookieName = "MyAuthCookie",
                CookieHttpOnly = true,
                CookieSecure = CookieSecureOption.Always,
                ExpireTimeSpan = TimeSpan.FromDays(30),
                SlidingExpiration = true
            });            
            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);    

Could it have something to do with the SecurityStampValidator?

Any and all help or suggestions are welcome. Thanks!