SearchPanes options are empty on the serverSide yajra dataTable

I tried to use the SearchPanes on the serverSide datatable, but It doesn't work; the SearchPanes options are empty.

public function getSalesReturnsData()
{

    $sales = Sale::query()
        ->select(DB::raw("Bestelldatum, kLieferscheinPos ,cBestellNr,
            Verkaufsplattform, SKU, GTIN, HAN, Hersteller, Lieferant, cName, 
            Menge, VKPreis, UVP, Farbe, Groesse, Warengruppe, Transaktion, 
            Anmerkung, Lieferland, Versandart, Zahlungsart, VersandkostenBrutto, 
             GutscheinBestellungBrutto"))
        ->where('Bestelldatum', '>', now()->subDays(30)->endOfDay());

    $returns = ProductReturn::query()
        ->select(DB::raw("Retourendatum, kRMRetoure,cBestellNr, Verkaufsplattform, 
            SKU, GTIN, HAN, Hersteller, Lieferant, cName, Menge, VKPreis, UVP, Farbe,
            Groesse, Warengruppe, Transaktion, Anmerkung, Lieferland, Versandart, 
            Zahlungsart, VersandkostenBrutto, GutscheinBestellungBrutto"));

    $results = $sales->unionAll($returns);


    return DataTables::of($results)
        ->addColumn('Bestelldatum', function ($row) {
            $bestelldatum = date("d.m.Y", strtotime($row->Bestelldatum));
            return $bestelldatum;
        })->make(true);
}

JavaScript

$(document).ready(function () {
    load_data();

    function load_data() {
        $('#datatable').DataTable({
            processing: true,
            serverSide: false,
            ajax: {
                url: "{{ route('getSalesReturnsData') }}"
            },
            "columns": [{
                "data": "Bestelldatum"
            },
                {
                    "data": "kLieferscheinPos"
                },
                {
                    "data": "cBestellNr"
                },
                {
                    "data": "Verkaufsplattform"
                },
                {
                    "data": "SKU"
                },
                {
                    "data": "GTIN"
                },
                {
                    "data": "HAN"
                },
                {
                    "data": "Hersteller"
                },
                {
                    "data": "Lieferant"
                },
                {
                    "data": "cName"
                },
                {
                    "data": "Menge"
                },
                {
                    "data": "VKPreis"
                },
                {
                    "data": "UVP"
                },
                {
                    "data": "Farbe"
                },
                {
                    "data": "Groesse"
                },
                {
                    "data": "Warengruppe"
                },
                {
                    "data": "Transaktion"
                },
                {
                    "data": "Anmerkung"
                },
                {
                    "data": "Lieferland"
                },
                {
                    "data": "Versandart"
                },
                {
                    "data": "Zahlungsart"
                },
                {
                    "data": "VersandkostenBrutto"
                },
                {
                    "data": "GutscheinBestellungBrutto"
                },
            ],
            dom: 'PBfrtip',
            stateSave: true,
            searchPanes: {
                initCollapsed: true,
                cascadePanes: true,
                dtOpts: {
                    paging: 'flase',
                    pagingType: 'simple',
                    select: {
                        style: 'multi'
                    }
                },
                columns: [3, 5, 8, 6, 7, 9, 11, 16]
            }
        });
    }

});