Add style to selectpicker selectlist

I have a selectpicker list with initial style but when is populated the style is not applyed and I cannot change it using methods mentioned below

    Tip masura
    
    Selecteaza tipul masurii
    
    
    
    
    

    Masura de protectie
    
    Selecteaza masura
    
    
    
                        
    
    

and json for populating the select list

$(function () {
            $("#TipMasura").on("change", function () {
                var categoryId = $("#TipMasura :selected").text();
                $("#Masura").empty();
                $("#Masura").append("--Selecteaza o masura existenta--");
                $("#Masura").append("--Adauga o masura noua--");
                $.getJSON(`?handler=Masura&id=${categoryId}`, (data) => {
                    $.each(data, function (i, item) {
                        $("#Masura").append(`${item.text}`);
                    });
                    $('#Masura').selectpicker({ liveSearch: true });
                    $("#Masura").selectpicker('refresh');
                    $("#Masura").addClass("sMasura")
                });
                
                var data = $("#TipMasura :selected").text();
                $("#txtTM").val(data);
            });
        });

        $(function () {
            $("#Masura").on("change", function () {
                var data = $("#Masura :selected").text();

                if (data == "--Selecteaza o masura existenta--") {
                    $("#AddNew").attr("hidden", true);
                    $("#txtMasura").val("");
                }
                else if (data == "--Adauga o masura noua--") {
                    $("#AddNew").attr("hidden", false);
                    $("#txtMasura").val("");
                }
                else {
                    $("#AddNew").attr("hidden", true);
                    $("#txtMasura").val(data);
                }
            });
        });

and css

I also tried $("#Masura").css("height", "50") but no results