I wrote simple code as below for receiving data via CANbus. I have a board and a CANbus analyzer for testing. I send data from analyzer to the board. In debug mode I saw that the data is received correctly, the data_received variable is set to 1 too, but the b variable has not changed. It seems that we don't come out of the interrupt function and don't come to while(1).

#include "main.h"

CAN_HandleTypeDef hcan1;
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_CAN1_Init(void);
CAN_RxHeaderTypeDef RxHeader;
uint8_t data[2];
volatile int data_received=0;
volatile int b=0;

void HAL_CAN_RxFifo0MsgPendingCallback(CAN_HandleTypeDef *hcan)
{
    if(hcan->Instance==CAN1)
    {
        HAL_CAN_GetRxMessage(hcan,CAN_RX_FIFO0,&RxHeader,data);
    }

    if (RxHeader.DLC==2)
    {
        data_received=1;
    }
    else
    {
        data_received=0;
    }
}


int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_CAN1_Init();

  if (HAL_CAN_Start(&hcan1) != HAL_OK)
  {
    Error_Handler();
  }

  if (HAL_CAN_ActivateNotification(&hcan1, CAN_IT_RX_FIFO0_MSG_PENDING)!= HAL_OK)
  {
    Error_Handler();
  }


  while (1)
  {
      if (data_received==1)
      {
          b=1;
          data_received=0;
      }
  }
}

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 25;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 4;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
  {
    Error_Handler();
  }
}

static void MX_CAN1_Init(void)
{

  hcan1.Instance = CAN1;
  hcan1.Init.Prescaler = 3;
  hcan1.Init.Mode = CAN_MODE_NORMAL;
  hcan1.Init.SyncJumpWidth = CAN_SJW_1TQ;
  hcan1.Init.TimeSeg1 = CAN_BS1_11TQ;
  hcan1.Init.TimeSeg2 = CAN_BS2_2TQ;
  hcan1.Init.TimeTriggeredMode = DISABLE;
  hcan1.Init.AutoBusOff = DISABLE;
  hcan1.Init.AutoWakeUp = DISABLE;
  hcan1.Init.AutoRetransmission = DISABLE;
  hcan1.Init.ReceiveFifoLocked = DISABLE;
  hcan1.Init.TransmitFifoPriority = DISABLE;
  if (HAL_CAN_Init(&hcan1) != HAL_OK)
  {
    Error_Handler();
  }

  CAN_FilterTypeDef canfilterconfig;

  canfilterconfig.FilterActivation = CAN_FILTER_ENABLE;
  canfilterconfig.FilterBank = 18;
  canfilterconfig.FilterFIFOAssignment = CAN_RX_FIFO0;
  canfilterconfig.FilterIdHigh = 0x103<<5;
  canfilterconfig.FilterIdLow = 0x0000;
  canfilterconfig.FilterMaskIdHigh = 0x103<<5;
  canfilterconfig.FilterMaskIdLow = 0x0000;
  canfilterconfig.FilterMode = CAN_FILTERMODE_IDMASK;
  canfilterconfig.FilterScale = CAN_FILTERSCALE_32BIT;
  canfilterconfig.SlaveStartFilterBank = 20;
  HAL_CAN_ConfigFilter(&hcan1, &canfilterconfig);

}

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOE_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  HAL_GPIO_WritePin(GPIOE, GPIO_PIN_11, GPIO_PIN_SET);

  GPIO_InitStruct.Pin = GPIO_PIN_11;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);
}

void Error_Handler(void)
{
  __disable_irq();
  while (1)
  {
  }
}

#ifdef  USE_FULL_ASSERT
void assert_failed(uint8_t *file, uint32_t line)
{
  
}
#endif