CCS/TMS320F28021: watchDog can't software reset

Tool/software: Code Composer Studio

      I have two codes from TMS32F28021,code one:start bootloader code,code two:app code.my application is app's watchdog reset run to code one,than run to app code,on time is ok,but two times app's watchdog can't reset.can you help me,thank!

      other one,code one watchdog working normal,i think that code is ok.

      end,i want to discribtion my watchdog code from app,

      app code:

main()

{

//    EALLOW;
//    SysCtrlRegs.WDCR= 0x0068;
//    EDIS;

disbaledog();

........

//    EALLOW;
//    SysCtrlRegs.WDCR= 0x002F;
//    EDIS;

enabledog();

.........

while(1)

{

KickDog();

         .......

}

}

__interrupt void cpu_timer0_isr(void)

{

........

else if(SW_Upadte_Flag==4)

{SW_Upadte_Flag = 5;