Display Model State error after jQuery Ajax call in ASP.Net Core MVC

Hi,

I have created one form where i am saving the data using form, but when submit form and my ModelState is getting invalid and still i am not getting error message. 

Please check and let me know what is wrong with my code.

public IActionResult Index(Student model)
{ 
    if (ModelState.IsValid)
    {
        ProviderPersonalInfoUpdate modelinfo = new ProviderPersonalInfoUpdate();
        modelinfo.UserId = model.ManageProvider.UserId;
        modelinfo.FirstName = model.ManageProvider.FirstName;
        modelinfo.MiddleName = model.ManageProvider.MiddleName;
        modelinfo.LastName = model.ManageProvider.LastName;
        modelinfo.DOB = dtdob;
        modelinfo.Email = model.ManageProvider.Email;
        modelinfo.StartDate = dtstartdate;
        modelinfo.TaxID = model.ManageProvider.TaxID;
        modelinfo.PTan = model.ManageProvider.PTan;
        modelinfo.NPI = model.ManageProvider.NPI;
        modelinfo.SSN = model.ManageProvider.SSN;
        modelinfo.Phone = model.ManageProvider.Phone;
        modelinfo.Fax = model.ManageProvider.Fax;
        modelinfo.AddressLine1 = model.ManageProvider.AddressLine1;
        modelinfo.AddressLine2 = model.ManageProvider.AddressLine2;
        modelinfo.StateID = model.ManageProvider.StateID;
        modelinfo.CityID = model.ManageProvider.CityID;
        modelinfo.Zipcode = model.ManageProvider.Zipcode;
        modelinfo.Website = model.ManageProvider.Website;
        modelinfo.UserId = HttpContext.Request.Cookies["UserId"] != null ? HttpContext.Request.Cookies["UserId"].ToString() : "";
        AccountApiCall accountApiCall = new AccountApiCall(Configuration["ABCAPI"]);
        model.ManageProvider.createdBy = HttpContext.Request.Cookies["FullName"] != null ? HttpContext.Request.Cookies["FullName"].ToString() : "";
        var Response = accountApiCall.PostAPIcall<GetProviderDetailModel>(modelinfo, "provider/personaldetailsupdate", HttpContext.Request.Cookies["Token"].ToString());            
        if (Response.status)
        {                 
            TempData["ProviderId"] = model.ManageProvider.UserId;
            TempData.Keep("ProviderId");
 
            return Json(Response);
        }
        else
        {
            return Json(Response);                  
        }
    }
    else
    {
        return View("Index");                        
    }
}

this is controller where i am getting ModelState invalid but still no error message is displaying