Enumerator that indicates all possible error conditions found during the processing of the request. 
| Enumerator | 
|---|
| ConnectionRefusedError |  | 
| RemoteHostClosedError | The remote server refused the connection (the server is not accepting requests).  | 
| HostNotFoundError | The remote server closed the connection prematurely, before the entire reply was received and processed.  | 
| TimeoutError | The remote host name was not found (invalid hostname).  | 
| OperationCanceledError | The connection to the remote server timed out.  | 
| SslHandshakeFailedError | The operation was canceled.  | 
| TemporaryNetworkFailureError | The SSL/TLS handshake failed and the encrypted channel could not be established.  | 
| NetworkSessionFailedError | The connection was broken due to disconnection from the networkd.  | 
| BackgroundRequestNotAllowedError | The connection was broken due to disconnection from the network or failure to start the network.  | 
| ProxyConnectionRefusedError | The background request is not currently allowed due to platform policy.  | 
| ProxyConnectionClosedError | The connection to the proxy server was refused (the proxy server is not accepting requests. )  | 
| ProxyNotFoundError | The proxy server closed the connection prematurely, before the entire reply was received and processed.  | 
| ProxyTimeoutError | The proxy host name was not found (invalid proxy hostname).  | 
| ProxyAuthenticationRequiredError | The connection to the proxy timed out or the proxy did not reply in time to the request sent.  | 
| ContentAccessDenied | The proxy requires authentication in order to honour the request but did not accept any credentials offered.  | 
| ContentOperationNotPermittedError | The access to the remote content was denied.  | 
| ContentNotFoundError | The operation requested on the remote content is not permitted.  | 
| AuthenticationRequiredError | The remote content was not found at the server.  | 
| ContentReSendError | The remote server requires authentication to serve the content but the credentials provided were not accepted.  | 
| ProtocolUnknownError | The request needed to be sent again, but this failed.  | 
| ProtocolInvalidOperationError | The Network Access API cannot honor the request because the protocol is not known.  | 
| UnknownNetworkError | The requested operation is invalid for this protocol.  | 
| UnknownProxyError | An unknown network-related error was detected.  | 
| UnknownContentError | An unknown proxy-related error was detected.  | 
| ProtocolFailure | An breakdown in protocol was detected. A breakdown in protocol was detected.  |