I'm getting the following error when I run FtpClient.Connect(serverName: host, serverPort: 21, parameters: tls, security: FtpSecurity.Explicit);

Rebex.Net.TlsException: Fatal error 'HandshakeFailure' has been reported by the remote connection end.
   at wWGvS.AsKBXeZ.OnAlertReceived(Byte[] buffer, Int32 offset, Int32 count)
   at wWGvS.ckSCApZ.BdFvlW(Byte[] , Int32 , Int32 )
   at wWGvS.ckSCApZ.cDtmAOZ()
   --- End of inner exception stack trace ---
   at wWGvS.ckSCApZ.cDtmAOZ()
   at wWGvS.ckSCApZ.ArwjUr()
   at Rebex.Net.TlsSocket.Negotiate()
   at wWGvS.AgXIfM.AUXDmhZ(TlsParameters )
   at Rebex.Net.Ftp.BLyBkd(TlsParameters , FtpSecureUpgradeType )
   at Rebex.Net.Ftp.Connect(String serverName, Int32 serverPort, TlsParameters parameters, FtpSecurity security)

tls parameters are:

TlsParameters tls = new TlsParameters
{
    AllowedSuites = TlsCipherSuite.All,
    Certificate = certChain,
    Version = TlsVersion.Any,
    CertificateVerifier = new CustomVerifier(),
    CertificateRequestHandler = CertificateRequestHandler.StoreSearch
};