When I use STM32F042F6P6 for initialization, it doesn't come out here, and IO is redirected to PA11 and PA12. Why?

while (((CANx-> MSR & CAN_MSR_INAK) == (uint16_t) CAN_MSR_INAK) && (wait_ack! = INAK_TIMEOUT))
{
wait_ack ++;
}
Who can teach me?