: The RS232 or USB-to-UART cable may not be connected properly, or the TX/RX pins are swapped.

Follow these sequential blocks to resolve the connection barrier. 1. Audit the Physical Wiring

: Loose RX/TX wires, incorrect cross-wiring (TX should go to RX and vice versa), or a faulty USB-to-TTL adapter.

Help you find the if you tell me your box's exact model number .