The following error can be caused by firewall restrictions. I do not know the specifics of the firewall restrictions, but the TLS connection completes successfully in the prior call to Chilkat.Rest.Connect(). In other words, the TLS handshake completes successfully and then the firewall closes (or blocks) the connection.
ChilkatLog: FullRequestFormUrlEncoded: DllDate: Jul 24 2019 ChilkatVersion: 188.8.131.52 UnlockPrefix: Start my 30-day Trial Architecture: Little Endian; 32-bit Language: ActiveX VerboseLogging: 0 uriPath: /api/security/oauth/token autoReconnect: 1 sendReqFormUrlEncoded: sendReqHeader: omitContentType: 0 sendReqHeader2: checkEstablishConnection: The connection already exists, as far as we know.. --checkEstablishConnection --sendReqHeader2 --sendReqHeader --sendReqFormUrlEncoded fullRequestGetResponse: Reading response header... Failed to read beginning of SSL/TLS record. b: 0 dbSize: 0 nReadNBytes: 0 idleTimeoutMs: 30000 Failed to receive more TLS application data. tlsApp: Socket operation timeout. elapsedMs: Elapsed time: 30919 millisec Failed. Failed to read response header. --fullRequestGetResponse Failed. --FullRequestFormUrlEncoded --ChilkatLog