CCS/MSP430FR4133: Watchdog timer interrupt handling

Part Number: MSP430FR4133

Tool/software: Code Composer Studio

I would like to toggle an LED at interval of 1 second . Therefore I implemented the coding below . However , I could not observe any toggling most probably due to the fact that WDTIFG  is never raised. I read the documentation of MSP4133 over and over again and I am aware of that WDTIE and GIE have to be set so as to raise WDTIFG.  There must be something I am missing .

Another issue is that I had previously inserted WDTSSEL1 since it is 01b should have corresponded to ACLK(32kHz) .However , I realized that it was set as 10b in the registers window upon that I tried WDTSSEL0 and it  yielded 01b . It did not make sense for me. If anyone could explain it , I would appreciate . Thanks in advance !. 

#include <msp430.h> 
#define LED BIT0

int main(void)
{
	WDTCTL = WDTPW | WDTTMSEL | WDTSSEL0 | WDTCNTCL; 	// interval timer mode is selected,  ACLK selected 32khz  watch dog timer 1/32kHz * 32.768 = 1 second WDT period


	P1DIR |= LED;       //P1.0 is defined as output
	P1OUT &= ~LED;      //LED at P1.0 is turned off initially
	PM5CTL0 &= ~LOCKLPM5;   //previous port settings are activated.

	SFRIE1 |= WDTIE;        // Enable WDT interrupt
	__bis_SR_register(GIE);  //general interrupts enabled.


	for(;;){

	    if((SFRIFG1 & WDTIFG) !=0){
	    //toggle LED once interrupt raised.
	        P1OUT ^= LED ; // toggles LED otherwise
	        WDTCTL = WDTPW | WDTTMSEL | WDTSSEL0 | WDTCNTCL; //watchdog timer starts over counting once again upto limit.
	        //WDTIFG is single source interrupt flag therefore automatically resets when it is serviced.

	    }
	    }

	return 0;
}