Open new window when returning AJAX information

I am trying to send information by AJAX to a PHP and when the response returns, another PHP opens in another tab that will process the returned information.

I have this code

function printAdmLetter()
{
    if($("#adm_nomina").val()==""||$("#case_desc").val()==""||$("#boss_actions").val()==""||$('select[name=cause]').val()==null)
    {
        swal("¡Olvidaste algo!", "La información no está completa.", "error");
        return false;
    }

    else
    {
        adm_nomina = document.getElementById("adm_nomina").value;
        auth = document.getElementById("auth").value;
        cause = $('select[name=cause]').val();
        case_desc = document.getElementById("case_desc").value;
        boss_actions = document.getElementById("boss_actions").value;
        $.ajax(
        {

            url:"./phpLibraries/admLetter.php",
            method:"POST",
            data:{adm_nomina:adm_nomina,
                        auth:auth,
                        cause:cause,
                      case_desc:case_desc,
                    boss_actions:boss_actions},
            success:function(data)
            {
                if(data=='X')
                {
                    swal("¡Error!","No se pudo ingresar la información, intentalo nuevamente.","error");
                }

                else
                {
                        window.open('phpLibraries/printAdmLetter.php?id='+data);
                }
            }
     });
    }
}

The problem is that it doesn't do anything, it doesn't open the tab. I did a test with:

window.location.href='phpLibraries/printAdmLetter.php?id='+data;

and that way it works.