RS-CAN(RH850-F1M): Can't transmit using TX buffer (can't write to TMTR bit in RSCAN0TMCp register)

I am trying to send data out from RS-CAN TX Buffers in RH850-F1M. Hence I did the following steps:-

1. Stored data in the TX buffers. 

/* Transmission from Transmit Buffers */
/* Store the messages in the Transmit uffers. */
for (p=0; p<=95; p++){
/* Set buffer ID */
HWREG_RD(RSCAN0TMIDp(p)) = (HWREG_RD(RSCAN0TMIDp(p)) & 0xe0000000u) | 0x3ffu;

/* Set buffer DLC data, buffer label */
HWREG_RD(RSCAN0TMPTRp(p)) = (HWREG_RD(RSCAN0TMPTRp(p)) & 0x0fffffffu) | 0x80000000u;

/* Set the transmit buffer data */
HWREG_RD(RSCAN0TMDF0p(p)) = 0xdeadbeefu;
HWREG_RD(RSCAN0TMDF1p(p)) = 0xdeadbeefu;


2. Request to transmit data

/* Request transmission for Channel3 */
/* for (p=48; p<=16*3+15; p++){ */
for (p=0; p<=95; p++){


Problem, is I see the TX buffer data updated to the values, but TMTR in RSCAN0TMCp(p) always remains at value: "Not Requested". Kindly, help me as to why am I not able to change the value of this bit ?

NOTE: I have checked the base addresses and register offset and they are correct.