KC868-A4 ,RS232 can not communicate with Max232

[Nantawit]

Could  you  help  me  about  rs232 port for your  product  that  desighed  RS232 female  on board  so I  want  to  connect  with  modbus 485 devices that  is  ,must  convert  rs232 to  TTL (use max232) nad  then use  max 485  so  I  try  to connect  but  can  not  show  the  data  Rx ,TX .
          firstly ,testing  the rs232  alone  by  pin 2 (tx)  connect  to  LED series with resistor 1 k  the  result  was  LED  blinking and  also  verified by  connecting pin RX and TX together  then  checking  the  serial monitor  so  its  can shows the  data  and  then conneecting  rs232 with Max 232 after that the  result  can  not  show  as the  last .