PGP BouncyCastle + Kleopatra Decryption: Unknown Packet Type: 20

Question

I am attempting to decrypt a file using BouncyCastle in C# that has been encrypted with RSA via Kleopatra. Unfortunately, I am receiving an error that states "Unknown packet type encountered: 20" when processing through the first few lines of decryption. The (pseudo) code:

   using (Stream inputStream = File.OpenRead(test.txt.gpg))
   {
       using (Stream keyIn = File.OpenRead(privatekey.asc))
       {
                PgpObject o = null;

                PgpObjectFactory pgpF = new PgpObjectFactory(PgpUtilities.GetDecoderStream(inputStream));
                
                PgpSecretKeyRingBundle pgpSec = new PgpSecretKeyRingBundle(PgpUtilities.GetDecoderStream(privateKeyStream));

                if (pgpF != null)
                {
                    o = pgpF.NextPgpObject(); -- THIS LINE THROWS THE UNKNOWN PACKET TYPE ERROR
                }
       }
   }

After googling, I have seen examples that the above code snippet models, but I have not yet seen any information about unknown packet types.

Does anyone know if I am doing anything wrong, or can point me in the direction of documentation of the error code numbers?

Thank you in advance for your time.