If dealing with a brand new never before tested hardware design it's recommended to gradually add wires between vehicle connector breakout board and untested ECU.
1. Test & Report, with USB physically disconnected: Attempt cranking. If equipped with on-board persistent storage, upload & link log to report.
1. Connect ECU to laptop via serial, report type of serial.
1. With laptop connected via serial, test & Report, with USB physically disconnected: ECU status LED blinks if powered up, ECU status LED blinks when ignition powered off.