serial communication between two tinker boards with hardware flow control enabled using rs232 cable

[skyrock123 0]

 I want your help regarding tinker board r2.0 about GPIO pins, let me explain what I'm trying to do 

I want to send and receive data through two tinker boards from the port ttyS1 with hardware flow control enabled 

both boards have same configuration of serial port ttyS1 and hardware flow is enabled but when I send data through a board using python--

import serial

ser = serial.Serial('/dev/ttyS1', baudrate=9600, rtscts=True)

# Print initial RTS and CTS status
print("RTS:", ser.rts)
print("CTS:", ser.cts)

# Transmit data
ser.write(b'Hello')

# Print RTS and CTS status after transmission
print("RTS:", ser.rts)
print("CTS:", ser.cts)

I'm getting the output showing O/P = (CTS = False) before and after data transmission each and every time I execute it, and in the other board I can't see any data incoming in minicom and this is vice versa for the other board. I have connected GP5B1(TX) , GP5B0(RX) , VCC, GND, GP5B2(CTS) and GP5B3(RTS) in both boards through RS232 cable .

But when I connect the ttyS1 to USB of my windows laptop and send data through dock light with hardware flow control enabled I'm able to send and receive data

The issue occurs when I connect two tinker boards with rs232

Please help me with this problem..