Attiny204 Interrupt Flag Not Being Generated - interrupt

Question

I'm trying to write a (fairly) basic bit of software for and Attiny204, which handles interrupts when a clock input is pulled high.
When I run the code in the debug simulator in Atmel Studio, and set the clock input high, there is no interrupt flag generated. The interrupts do trigger when I manually produce an interrupt flag.
I've tried using different pins, and even, the other port. I can't seem to get the simulator to produce the interrupt flag.
In the past, I have used the AtMega328P in the simulator with equivalent code, and it works fine.
ISR(PORTA_PORT_vect)
{
//In this function we must:
//1. Shift all data up
shiftUp();
//2. Get new 8th bit
bit8 = VPORTA.IN & (1 << 1);
//3. Set Data Output Pin to bit0
if(bit0 == 0)
VPORTA.OUT &= ~(1 << 3);
else
VPORTA.OUT |= (1 << 3);
//4. Calculate new dimValue and dimMilliseconds
calcDim();
calcDelay();
}
int main(void)
{
initVariables();
/*
Below this, we must set the Data Direction (DD) of each pin we assigned.
*/
//Below, set the ISC of the Zero Cross Pin and the Clock Pin to allow interrupts
PORTA_PIN0CTRL |= 0b00000001; //Zero Cross
//PORTA_PIN1CTRL = 0b00000000; //Data In
//PORTA_PIN2CTRL = 0b00000000; //Data Next
//PORTA_PIN3CTRL = 0b00000000; //Triac Control
PORTB_PIN0CTRL |= 0b00000001; //Clock
//VPORTB.INTFLAGS |= 0b00000001;
//Set Port direction.
VPORTA.DIR = 0x30;
VPORTB.DIR = 0x00;
/*
Below this, we must enable interrupts.
*/
sei();
/* Replace with your application code */
while (1)
{
}
}

Answer 1

Why are you writing to VPORTA and VPORTB? The Tiny204 doesn´t have this registers.
You enable interrupts on both edges for Pin 0 of Port A (PIN0CTRL bit 0 is set = BOTHEDGES) and you don´t clear the interrupt flag in your ISR of Port A. Please take a look at the data sheet:
The interrupt request remains active until the interrupt flag is cleared. See the peripheral's INTFLAGSregister for details on how to clear interrupt flags.