Connecting with Zoho CRM via API error

Hi support,

I am trying to connect with Zoho CRM via API C#, but I have an error during run the method(System.NullReferenceException: 'Object reference not set to an instance of an object.'),

I think there is something wrong with the configuration

could you please help me

at ZCRMSDK.CRM.Library.CRMException.ZCRMLogger.LogError(String message)

at ZCRMSDK.CRM.Library.CRMException.ZCRMLogger.LogError(Exception exception)

at ZCRMSDK.CRM.Library.Api.Handler.OrganizationAPIHandler.GetUsers(String type, String modifiedSince, Int32 page, Int32 perPage)

at ZCRMSDK.CRM.Library.Setup.MetaData.ZCRMOrganization.GetAllUsers()

at Test_Zoho_New.Form1.GetAllUsers() in C:\Users\ahlwani\source\repos\Test_Zoho_New\Form1.cs:line 36

at Test_Zoho_New.Form1.Button1_Click(Object sender, EventArgs e) in C:\Users\ahlwani\source\repos\Test_Zoho_New\Form1.cs:line 28

at System.Windows.Forms.Control.OnClick(EventArgs e)

at System.Windows.Forms.Button.OnClick(EventArgs e)

at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)

at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)

at System.Windows.Forms.Control.WndProc(Message& m)

at System.Windows.Forms.ButtonBase.WndProc(Message& m)

at System.Windows.Forms.Button.WndProc(Message& m)

at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)

at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)

at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)

at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)

at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)

at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)

at System.Windows.Forms.Application.Run(Form mainForm)

at Test_Zoho_New.Program.Main() in C:\Users\ahlwani\source\repos\Test_Zoho_New\Program.cs:line 19