It sounds like your TLS setup is basically correct, since the handshake works via OpenSSL, so the issue is likely on the CODESYS side rather than the certificates themselves. From what I’ve seen with the Azure IoT Hub Client SL library, you should double-check that the SAS token is actually being generated and passed correctly to the function blocks (especially wsDeviceSaS) and that the MQTT/HTTPS FB is really triggered cyclically-otherwise the controller won’t initiate the connection at all. Also,...