ASP.NET Request time out calling an async webmethod in ASMX from jquery

I can't figure this out in days. I have tried everything. I have to change my cloud storage so I'm trying to refactor. First of all, I'm using MinIO in an intermediate class to connect the storage.

S3ObjectStorage.cs

public class S3ObjectStorage
{
    private MinioClient _client;
    private string _bucketName;

    public S3ObjectStorage(string key, string secret, string region, string httpsEndPoint, string bucketName) {
        _client = new MinioClient(httpsEndPoint, key, secret, region).WithSSL();
        _bucketName = bucketName;
    }

    public async Task<string> ListFilesAsync(string path)
    {
        return await ListObjects(path, false);
    }

    private async Task<string> ListObjects(string path, bool isDir) {
        var files = await _client.ListObjectsAsync(_bucketName, path)
            .Where<Item>(f => (isDir) ? (f.Key.EndsWith("/") && f.IsDir) : !f.Key.EndsWith("/"))
            .ToList();
        return Newtonsoft.Json.JsonConvert.SerializeObject(files);
    }
}

TestPage.aspx.vb (runs properly)

Public Class TestPage
    Inherits Page

    Protected Async Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
        cs = New S3ObjectStorage(CS_KEY, CS_SECRET, CS_REGION, HTTPS_ENDPOINT, BUCKET_NAME)
    End Sub

    Private Async Function List(path As String) As Task
        Dim resultFiles As String = Await cs.ListFilesAsync(path)
        Dim files = Newtonsoft.Json.JsonConvert.DeserializeObject(resultFiles)
        Me.rptFiles.DataSource = files
        Me.rptFiles.DataBind()
    End Function

End Class

Later I will try to use another technology, but for now, I need to use a webmethod in an ASMX to modify the code as little as possible. With the other cloud storage, all methods were synchronous, but MinIO doesn't.

index.aspx

<script type="text/javascript" language="javascript">
function listFiles() {
    $.ajax({
        type: 'POST', contentType: "application/json; charset=utf-8", dataType: 'json', async: true,  
        url: '/WS/WSFileManager.asmx/ListFiles',
    ...);

WSFileManager.asmx.vb (trying 2 ways)

    <WebMethod(EnableSession:=True)>
    <ScriptMethod(ResponseFormat:=ResponseFormat.Json)>
    Public Async Function ListFiles(signature As String, requestCode As String, previousDeleted As String) As Threading.Tasks.Task(Of String)

    'First way
    Dim minioClient As New MinioClient(GlobalConstants.S3_HTTPS_ENDPOINT,
                                           GlobalConstants.S3_KEY,
                                           GlobalConstants.S3_KEY,
                                           GlobalConstants.S3_REGION)
    minioClient.WithSSL()
    Dim files As New List(Of DataModel.Item)
    Dim observable As IObservable(Of DataModel.Item) = minioClient.ListObjectsAsync(GlobalConstants.S3_BUCKET_NAME, pathApp, False)
    Dim suscription As IDisposable = observable.Subscribe(
        Sub(item)
            files.Add(item)
        End Sub)
    suscription.Dispose()
    'files.Count always is 0
    
    'Second way
    Dim s3Storage As New S3ObjectStorage(GlobalConstants.S3_KEY, GlobalConstants.S3_SECRET,
                                        GlobalConstants.S3_REGION, GlobalConstants.S3_HTTPS_ENDPOINT,
                                        GlobalConstants.S3_BUCKET_NAME)
    Dim resultFiles As String = Await s3Storage.ListFilesAsync(pathApp)
'**Never reach this line**
....

My current cloud storage ends next January 31st, so I need the new one runs as soon as possible.

Thank you very much!