If both H8S2633R's are close together (short wires) then you do not need a to convert to RS232. the two H8S2633R's can be directly wired.
If they are far apart, more than a meter, then do you have a MAX232 of each H8S2633R?
Try getting one H8S2633R serial communications working to a PC com port, with the MAX232, using a terminal program. This is much easier to troubleshoot and debug. Once this works then connect the two H8S2633R's together.