OAuth2

Hello guys,
I am trying to build elixir wrap up for xero using oauth 2 , but I am getting some errors

22:31:36.404 [info]  TLS :client: In state :certify at ssl_handshake.erl:1768 generated CLIENT ALERT: Fatal - Handshake Failure
 - {:bad_cert, :unable_to_match_altnames}
** (OAuth2.Error) {:tls_alert, {:handshake_failure, 'TLS client: In state certify at ssl_handshake.erl:1768 generated CLIENT ALERT: Fatal - Handshake Failure\n {bad_cert,unable_to_match_altnames}'}}
    (oauth2 2.0.0) lib/oauth2/client.ex:312: OAuth2.Client.get_token!/4