If the port is correct, and if the UART is using 3.3V TTL logic level, then the above should work. You might try with XON/XOFF flow control (software only flow control), but I suspect if it were a software flow control problem, then you’d at least have seen some activity and it wouldn’t be completely blank.
If you happen to have an oscilloscope, then perhaps you could watch the RX and TX wires to see if it has a 3.3V square wave during times you expect data.