SSRS Sql Server Reporting Server Custom Security 2019 exception in Windows Server 2019 - vb.net

Question

I am facing problem with respect to SSRS(Sql Server Reporting Server) 2019 Custom security Exception in windows server 2019,
Getting error as sqlAuthCookie is null, sending WebRequest to Reportserver to generate sqlAuthCookie from VB.net code but server unable to generate Cookie.
Anything solution/help would be much appreciated
Tried sending request from Vb.net to SSRS windows server 2019
Getting Custom security exception error and sqlAuthCookie error also
VB.NET Code
Protected Overrides Function GetWebResponse(ByVal request As WebRequest) As WebResponse
Dim response As WebResponse = MyBase.GetWebResponse(request)
Dim cookieName As String = response.Headers("RSAuthenticationHeader")
' If the response contains an auth header, store the cookie
If Not (cookieName Is Nothing) Then
Dim webResponse As HttpWebResponse = CType(response, HttpWebResponse)
Dim authCookie As Cookie = webResponse.Cookies(cookieName)
' If the auth cookie is null, throw an exception
If authCookie Is Nothing Then
Throw New Exception("Unable to generate report - the Reporting Services Custom Security Extension is expected to be enabled in XB")
End If
' otherwise save it for this request
Me.AuthCookie = authCookie
' and send it to the client
End If
Return response
End Function
SSRS service code
//adding new GetUserInfo method for IAuthenticationExtension2
public void GetUserInfo(IRSRequestContext requestContext, out IIdentity userIdentity, out IntPtr userId)
{
userIdentity = null;
if (requestContext.User != null)
{
userIdentity = requestContext.User;
}
// initialize a pointer to the current user id to zero
userId = IntPtr.Zero;
}