SAML Signature validation failed in ASP.NET when Assertion Signature signed

my client is using OKTA for SSO for my ASP.NET application, my app is using below code to validate the
signature to authenticate the SAML request. this is working fine if “Assertion signature” is unsigned. when it changes to signed it is failing. Do i need to handel it differently in .NET side?

Names space using : “System.Security.Cryptography.X509Certificates”

XmlDocument xDoc = new XmlDocument();
xDoc.PreserveWhitespace = true;
samldata = samldata.Replace(@"", “”);

           var xDoc2 = GetDecryptedAssertion(certificate, xDoc);

           using (var store = new X509Store(StoreName.My, StoreLocation.LocalMachine))
          var cert = store.Certificates.Find(X509FindType.FindBySubjectName, samlcert, true);
          if (cert.Count == 0)
                throw new Exception("Saml certificate not found");
          verificationCertification = cert[0];


   XmlNodeList nodeList = xDoc.SelectNodes("//ds:Signature", xMan);
   SignedXml signedXml = new SignedXml(xDoc);
   status = signedXml.CheckSignature(verificationCertification, true);

Was your problem resolved? I have a similar issue in C#