Function Pointer in C Struct

I have a struct in custom C code that I included in my state_flow simulation:

typedef struct __UART_Message_Queue{
	Queue_Lock 					lock;
	int8_t 						queue_front;
	int8_t 						queue_back;
	uint32_t 					message_queue[16];
	Queue_Status (* queue_push)(struct __UART_Message_Queue * queue, uint16_t header, uint16_t message);
	uint32_t (* queue_pop)(struct __UART_Message_Queue * queue);
	Queue_Status (* queue_status)(struct __UART_Message_Queue * queue);
}UART_Message_Queue;

and a function that I like to point to:

Queue_Status __queue_push(UART_Message_Queue* queue, uint16_t header, uint16_t message){
	if(queue->queue_status(queue)==QUEUE_FULL){
		return QUEUE_FULL;
	}
	else{
		queue->queue_back = (queue->queue_back + 1) % 16;
		queue->message_queue[queue->queue_back] = (((uint32_t)header)<<16U) + (uint32_t)message;
		return QUEUE_NOT_FULL;
	}
}

In my stateflow diagram, I assign:

UART_Message_Queue uart_queue;
uart_queue.queue_push = &__queue_push;

then when I call the "uart_queue.queue_push" function I get an error that the function is unresolved, but if I call the "__queue_push" everything is fine.

Has anybody faced this situation before?