ajax触发错误功能甚至响应有效json和状态200

I am using windows server 2012 and i built web app it was working fine on my local PC

but when I uploaded the code to sever the JQuery ajax function firing error function?

I did search around to find out what is the problem but no thing help

I added dataType:"text" and it fire the success function but it does not deal with the returned data as JSON. while when I added dataType:"json" it kept firing the error function

    $.ajax({
    url:url,
    type:"POST",
    data:{collegeID: ID},

    success:function(res){
     if(res.success == 1){
       trigger.append("<OPTION value=''>--Select Teacher--</OPTION>");
       $.each(res.data,function(){
        trigger.append(
            "<OPTION VALUE='"+this.teacher_id+"'>"+this.teacher_name_e+" | "+this.teacher_name_a+"</OPTION>"
        );
       });
     }else{
       trigger.append("<OPTION></OPTION>");
     }
     console.log(res);
    },
    error:function(e){
     trigger.append("<OPTION></OPTION>");
     console.log(e);
    }
});

response without adding dataType or with add dataType:"json"

response when I add dataType:"text"