I'm getting the same error on both projects (APNS Sharp | Push Sharp)
Authentication failed because remote party has closed the transport stream
I've tried with changing X509Certificate to X509Certificate2 and X509CertificateCollection to X509Certificate2Collection. I have also tried with .Ssl3 to .tls or .Default! i have tried various solution but my error remains the same. I am using .pem file as my certificate.