Selenium Webriver test using for load test ,recognize only first instance of the test and rest are giving error

I have a test using selenium C# webdriver chorme on windows 10. When i am running this test one at a time it is working fine. I am using the same test for loadtest in visual studio 2017. There I am am trying to run multiple instance of the same test. The first instance is always getting executed perfectly , but all the rest are not recognizing the web element and throwing the error mentioned below.

Test method LoadWebTestPOC.WebTestM.LoginWithCredentials threw exception: OpenQA.Selenium.WebDriverException: Unexpected error. System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 127.0.0.1:54049 at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception) --- End of inner exception stack trace --- at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context) at System.Net.HttpWebRequest.GetRequestStream() at

Could someone help me please. Thanks in advance.

I have seen similar issue here Selenium web driver fails after the first test run and TestFixtureTearDown happens

Here is the code how i am initializing the test

namespace LoadWebTestPOC
{
    [TestClass]
    public class WebTestM
    { 



    public string user = "Administrator";
    public string password = "*******";


    [TestInitialize]
    public void SetupTest()
    {
        Installer.SetUpEnv();
    }

    [TestCleanup]

    public void TeardownTest()
    {
        Base.QuitDriver();
    }

    [TestMethod]
    public void LoginWithCredentials()
    {
        LoginModule.NavigateTo();
        LoginModule.LoginWithCredentials(user,password);
        NUnit.Framework.Assert.AreEqual(user, CoreOperation.GetAttributeValue(LoginModuleLocators.iconLogedUser, "title")); 
    }
}
}


public static void SetUpEnv()
    {

     string _driver = CHROME;
     public static void SetupLocal(_driver)
    {
        switch (_driver)
                {
                    case "CHROME":
                        Base.Driver = Base.StartDriver(AvDriver.Chrome);
                        Base.ChosenDriverName = "chrome";
                        break;
                    case "FIREFOX":
                        Base.Driver = Base.StartDriver(AvDriver.Firefox);
                        Base.ChosenDriverName = "firefox";
                        break;
                    case "EDGE":
                        Base.Driver = Base.StartDriver(AvDriver.Edge);
                        Base.ChosenDriverName = "edge";
                        break;
                    case "SAFARI":
                        Base.Driver = Base.StartDriver(AvDriver.Safari);
                        Base.ChosenDriverName = "safari";
                        break;
                    default:
                        Base.Driver = Base.StartDriver(AvDriver.Chrome);
                        Base.ChosenDriverName = "chrome";
                        break;
                }
        }
    }


 public static IWebDriver StartDriver(AvDriver chosenDriver)
    {
        switch (chosenDriver)
        {
            case AvDriver.Chrome:
                Driver = new ChromeDriver(_driversPath);
                break;
            case AvDriver.Firefox:
                Driver = new FirefoxDriver(FirefoxDriverService.CreateDefaultService(_driversPath));
                break;
            case AvDriver.Edge:
                Driver = new EdgeDriver(_driversPath);
                break;
            case AvDriver.Safari:
                Driver = new SafariDriver();
                break;
        }

        Driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(10);
        Driver.Manage().Window.Maximize();
        return Driver;
    }