PCH warning: an unknown error occured

I am new to C++ and I am getting an odd error:

Error (active)      PCH warning: an unknown error occurred.  An IntelliSense PCH file was not generated.    CPPAssessment Chamber.cpp   1

This is my Chamber.cpp:

#include "stdafx.h"
#include "Chamber.h"

Chamber::Chamber(std::string text) {
    chamberDescription = text;
};

bool Chamber::hasHero() {
    return false;
};

void Chamber::showChamberOptions() {

};

And this is my Chamber.h:

#include <vector>
#include "Enemy.h"
#include "Hero.h"
#pragma once


class Chamber {

public:
    Chamber(std::string text);
    bool north;
    bool south;
    bool east;
    bool west;
    int x;
    int y;
    std::vector<Enemy> enemies;
    std::string chamberDescription;

    bool hasHero();

    void showChamberOptions();
private:

};

I can still run the program but everytime I go to this class in my IDE I get this error in the error list and we all hate errors of course!

Is there anything I can do to stop this? I read about adding pragma once but I already did that and I still receive the error.