Check the Null-Modem cable connection. Ensure it is a Null-Modem (crossed wires) cable, not a straight-through serial cable.
Pack modified files back into a flashable format (like .img or .fw files) for your device. Key Features and Compatibility New Tuxbox Flash Tool Download
Always run downloaded .zip or .rar files through VirusTotal. Check the Null-Modem cable connection