AJax call is not working going in error function

url is correct only

Parameters passing url, wbObj and TutorCoursedetails

Tutorcourse is in array format

var url = '@Url.Action("Managetutorupdate", "Common")';
/* saving values into database */
var msg = manageAddUpdate(url,wbObj,TutorcousePush);

function manageAddUpdate(url, wbObj, TutorcourseDetails) {
    var returnVal = '';
    try {
       
        $.ajax({
            type: 'POST',
            contentType: 'application/json; charset=utf-8',
            url: url,
            data: { 'wbObj': wbObj, 'TutorCourse': TutorcourseDetails },
            dataType: 'JSON',
            async: false,
            beforeSend: function () {
                $('#divPageLoading').show();
            },
            complete: function () {
                $('#divPageLoading').fadeOut(500);
            },
            success: function (data) {
                returnVal = data;
            },
            error: function (data) {
                returnVal = 'error';
            }
        });
    } catch (ex) {
        returnVal = 'error';
    }
    return returnVal;
}

public JsonResult Managetutorupdate(TutorProfileupdate wbObj,List<TutorProfileupdate> TutorCourse)
{
    string returnVal = string.Empty;
    return Json(returnVal, JsonRequestBehavior.AllowGet);
}

Could you please help me in this?