I have a problem reading ADC with DMA on STM32 F767zi. When I look into the buffer, all I see are zeros, and I do not know why?

Question

The size of my buffer is 4096 and I want to fill the buffer with the adc values that are read.

#define ADC_BUF_LEN 4096
uint16_t adc_buf[ADC_BUF_LEN];

I am using this function to start the reading process of the ADC using DMA

HAL_ADC_Start_DMA(&hadc2, (uint32_t*)adc_buf, ADC_BUF_LEN);

Here are my configurations for the ADC

 hadc2.Instance = ADC2;
  hadc2.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV6;
  hadc2.Init.Resolution = ADC_RESOLUTION_12B;
  hadc2.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc2.Init.ContinuousConvMode = ENABLE;
  hadc2.Init.DiscontinuousConvMode = DISABLE;
  hadc2.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc2.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc2.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc2.Init.NbrOfConversion = 1;
  hadc2.Init.DMAContinuousRequests = ENABLE;
  hadc2.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc2) != HAL_OK)
  {
    Error_Handler();
  }

This my DMA configuration

/**
  * Enable DMA controller clock
  */
static void MX_DMA_Init(void)
{

  /* DMA controller clock enable */
  __HAL_RCC_DMA2_CLK_ENABLE();

  /* DMA interrupt init */
  /* DMA2_Stream2_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA2_Stream2_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA2_Stream2_IRQn);

}

These are my interrupt functions. I set a toggle breakpoint on the first interrupt and when I debug, the LED does not turn on which suggests that the DMA isn't working?

/* USER CODE BEGIN 4 */
//Called when first half of buffer is filled
void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef* hadc) {
    //HAL_ADC_GetValue(&hadc2);

    HAL_GPIO_WritePin(LD3_GPIO_Port, LD3_Pin, GPIO_PIN_SET);
}

//Called when buffer is completely filled
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc){


    HAL_GPIO_WritePin(LD3_GPIO_Port, LD3_Pin, GPIO_PIN_RESET);
}

I set the prescaled to be divided by 6 if this information helps.

Please give me some advice! Thank you in advance.