HttpContext.Session.GetInt32() returns null - asp.net-mvc

Question

I have a simple Login form, where I set user Session data and redirect to Home page. This worked well before, but now in HomeController/Index, sessionID returns null and I'm not sure what caused this. It finds, that user is Authenticated, but doesn't get its ID.
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Login(LoginViewModel user)
{
if (ModelState.IsValid)
{
user.Password = Encryption.Encrypt(user.Password);
var checkLogin = _context.Users.FirstOrDefault(x => x.UserName.Equals(user.UserName) && x.Password.Equals(user.Password));
if (checkLogin != null)
{
HttpContext.Session.SetInt32("ID", checkLogin.ID);
HttpContext.Session.SetString("Name", checkLogin.Name);
HttpContext.Session.SetString("Surname", checkLogin.Surname);
HttpContext.Session.SetString("Role", checkLogin.Role.ToString());
var claims = new Claim[]
{
new Claim(ClaimTypes.Name, checkLogin.Name),
new Claim(ClaimTypes.Role, checkLogin.Role.ToString())
};
var identity = new ClaimsIdentity(claims, "AuthenticationCookie");
ClaimsPrincipal claimsPrincipal = new ClaimsPrincipal(identity);
//var authProperties = new AuthenticationProperties()
//{
// IsPersistent = true
//};
await HttpContext.SignInAsync("AuthenticationCookie", claimsPrincipal);
return RedirectToAction("Index", "Home");
}
else
{
ViewBag.Notification = " Wrong Username or Password";
}
}
return View();
}
Home:
[HttpGet]
public IActionResult Index()
{
var authenticated = HttpContext.User.Identity.IsAuthenticated;
if (authenticated)
{
int? sessionID = HttpContext.Session.GetInt32("ID");
int userCode = _context.Users.First(x => x.ID == sessionID.GetValueOrDefault()).UserCode;
if(userCode != 0)
{
_usersHelper.CheckForTemporaryManagers(userCode);
}
}
return View();
}
My Startup has all the required info:
public void ConfigureServices(IServiceCollection services)
{
services.AddDistributedMemoryCache();
string sessionId = Configuration.GetConnectionString("EndSequance");
services.AddSession(options =>
{
options.IdleTimeout = TimeSpan.FromMinutes(30);
options.Cookie.IsEssential = true;
options.Cookie.Name = sessionId;
options.Cookie.Path = "/" + sessionId;
});
services.AddHttpContextAccessor();