DOCSP-40417: Add X509 troubleshooting steps (#213)

(cherry picked from commit 3a03130)

Author: mcmorisi

source/connection-troubleshooting.txt

@@ -177,6 +177,34 @@ You can check if this is the issue by attempting to connect to a MongoDB
 instance hosted on the local machine with the same code. A deployment on
 the same machine doesn't require any authorization to connect.
 
+.. _csharp-troubleshooting-connection-X509:
+
+X.509 Credential Error
+~~~~~~~~~~~~~~~~~~~~~~
+
+If you are using Windows as your operating system, you might encounter an issue in which the
+{+driver-short+} is unable to locate an ``X.509`` authentication certificate in memory.
+This error is raised with the following error message:
+
+.. code-block:: none
+   :copyable: false
+
+   No credentials are available in the security package
+
+The following section describes a method that may help resolve the issue.
+
+Create and Store the Certificate On-Disk
+----------------------------------------
+
+Use the following code to generate any ``X.509`` certificates required by your application:
+
+.. code-block:: csharp
+
+   using (X509Certificate2 certWithKey = certOnly.CopyWithPrivateKey(key))
+   {
+      return new X509Certificate2(certWithKey.Export(X509ContentType.Pkcs12));
+   }
+
 Error Sending Message
 ~~~~~~~~~~~~~~~~~~~~~
 

source/fundamentals/authentication.txt

@@ -388,6 +388,13 @@ see the corresponding syntax for specifying the ``X.509`` authentication mechani
          You can alternatively pass ``null`` as the parameter to prompt the MongoDB
          server to infer the username based on your ``X.509`` certificate.
 
+.. note::
+
+   If you are using Windows, the driver might be unable to locate an ``X.509``
+   authentication certificate created in memory. To learn more about a potential solution to
+   this issue, see the :ref:`csharp-troubleshooting-connection-X509`
+   section of the Connection Troubleshooting guide.
+
 API Documentation
 -----------------