C# SSH.NET "ERROR: An established connection was aborted by the server"

I'm trying to connect to a server thru SSH.NET. It worked fine before but started to show "An established connection was aborted by the server" after some FW update on the server. Below is the code I'm using

private void HandleKeyEvent(object sender, AuthenticationPromptEventArgs e)
        {
            foreach (AuthenticationPrompt prompt in e.Prompts)
            {
                if (prompt.Request.IndexOf("Password:", StringComparison.InvariantCultureIgnoreCase) != -1)
                {
                    prompt.Response = "password";
                }
            }
        }
private void sshConnectBut_Click(object sender, EventArgs e)
        {
            var auth1 = new PasswordAuthenticationMethod("username", "password");
            var auth2 = new KeyboardInteractiveAuthenticationMethod("username");
            auth2.AuthenticationPrompt += new EventHandler<AuthenticationPromptEventArgs>(HandleKeyEvent);
            ConnectionInfo conInfo = new ConnectionInfo("Host", 22, "username", auth1, auth2);                
            
            this.sshClient = new SshClient(conInfo);
            this.sshClient.ConnectionInfo.Timeout = TimeSpan.FromSeconds(120);
            
            this.sshClient.Connect();   **<---- Error happened here**
        }

Can anyone help me on this issue please?

The report names no repository file or test; start by reviewing the ConnectionInfo setup and the failure at sshClient.Connect(). Use the comment thread to establish whether the firewall change, authentication methods, or server-side disconnect is reproducible, then document a confirmed cause and a regression test or minimal reproduction.