CCS: WTIMER : Cant Reset or assert (WTIMER1_TIMER_ICR) interrupt clear bit.

Tool/software: Code Composer Studio

I am using PC6 on my TM4c123gh6pm microntroller and the issue is that the code works and i am getting a time capture from Wtimer but in its ISR the flag is not setting. ? Code composer studio shows me (*) asteriks at that position and in watch window it shows me type as:  READNONE/WRITE NONE. Why is it doing that? Whats the problem and the solution.

void PeriodMeasure_Init(void){
	// Enable pin PC6 for WTIMER1 WT1CCP0=  WTimer1 A

  noInterrupts();


  SYSCTL_RCGCGPIO_R   |= (1<<2);       // activate port C CLOCK
  SYSCTL_RCGCWTIMER_R |= (1<<1);      // activate Wtimer1 CLOCK


//GPIOPinUnlockGPIO(GPIO_PORTC_BASE, GPIO_PIN_6);     // Unlock the PD7 GPIO



  GPIO_PORTC_DIR_R &= ~(1<<6);       // make PC6 input
  GPIO_PORTC_AFSEL_R |= (1<<6);      // enable alt funct
  GPIO_PORTC_DEN_R |= (1<<6);        // enable Digital Function

  GPIO_PORTC_PCTL_R = (GPIO_PORTC_PCTL_R & 0xF0FFFFFF)+0x07000000;  //Configured as WTimer on Pin6

  WTIMER1_CTL_R &= ~0x00000001;     // disable timer1A during setup

  WTIMER1_CFG_R = 0x00000004;       // configure for 32-bit capture mode
  WTIMER1_TAMR_R = 0x00000017;      // configure for rising edge event
  WTIMER1_CTL_R &= ~0x0000000C;     // rising edge
  WTIMER1_TAILR_R = 0x00000000;     // start value
  WTIMER1_TAPR_R = 0xFFFF;            // activate prescale, PreScaler Counts: 65535 Time to Reset: 3.518
  WTIMER1_IMR_R |= 0x00000004;      // enable capture match interrupt
  WTIMER1_ICR_R |= (1<<2);       // clear timer0A capture match flag //Clear Flag

  WTIMER1_CTL_R |= 0x00000001;      // timer0A 24-b, +edge, interrupts

  NVIC_PRI24_R = (NVIC_PRI24_R & 0xFFFFFF1F) | (1<<5); //WTimer1A->priority 1
  NVIC_EN3_R |= 0x1;             // enable interrupt 96 in NVIC
  interrupts();
}

void WideTimer1A_Handler(void){
if(FirstRun==1){
  WTIMER1_ICR_R = 0x00000004;       // clear timer0A capture match flag //Clear Flag

  Periodlong = (WTIMER1_TAR_R - INT_TIME) & 0xFFFFFFFF;  // 32-bit, 12.5ns resolution
  Time=Periodlong*12.5e-9;


  INT_TIME = WTIMER1_TAR_R;            // setup for next
          }

FirstRun = 1;                        // set semaphore
WTIMER1_ICR_R = 0x00000004;       // clear timer0A capture match flag //Clear Flag
}