Test Explorer cannot discover any unit tests in VS2019 - unit-testing

Question

I have .NET core unit test projects which use xunit package in Visual studio 2019, but I found that the unit tests cannot be discovered in the Test Exporer window, and there is below info in the Output-> Test pane.
I have tried the below workaround (from here) but none of them works
Update the VS2019 to the latest version (my version is 16.8.3)
Delete .vs folder then rebuild
Does anybody have any idea on this?
Microsoft.TestPlatform.VsTestConsole.TranslationLayer.TransationLayerException: C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\ServiceHub\Hosts\ServiceHub.Host.CLR.AnyCPU\ServiceHub.TestWindowStoreHost.exe process failed to connect to vstest.console process after 90 seconds. This may occur due to machine slowness, please set environment variable VSTEST_CONNECTION_TIMEOUT to increase timeout.
at Microsoft.TestPlatform.VsTestConsole.TranslationLayer.VsTestConsoleWrapper.WaitForConnection()
at Microsoft.TestPlatform.VsTestConsole.TranslationLayer.VsTestConsoleWrapper.EnsureInitialized()
at Microsoft.TestPlatform.VsTestConsole.TranslationLayer.VsTestConsoleWrapper.InitializeExtensions(IEnumerable`1 pathToAdditionalExtensions)
at Microsoft.VisualStudio.TestWindow.Messaging.RemoteAgent.BaseTestAgentBridge.InitializeExtensionsAsync(IEnumerable`1 extensions)
at Microsoft.VisualStudio.TestWindow.Host.TestPlatformAgentPool.<>c__DisplayClass21_0.<<CreateRemoteAgentAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.TestWindow.Utilities.EventPumpExtensions.<>c__DisplayClass4_0`1.<<EnqueueAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.TestWindow.Host.TestPlatformProvider.<UpdateRuntimeEnvironmentsAsync>d__32.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.TestWindow.Extensibility.ILoggerExtensions.<CallWithCatchAsync>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject)