Compiler Error C3646

#pragma once
#include <glew.h>
#define GLFW_INCLUDE_GLU
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include "GlslShader.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtx/transform.hpp>
using namespace std;
using namespace glm;
 
 
#include "loadimage.h"
 
 
class SkyBox {
public:
    void setup(string folder, float sizeSkyBox);
    void setupTexture(string folder);
    void setupGeometry();
    void update(mat4 MVP, vec3 pos);
    void draw();
private:
    GLuint textureID;
    GlslShader shader;
    mat4 MVP;
    mat4 modelMatrix;
    GLuint skyboxVAO, skyboxVBO;
    float sizeSkyBox;
 
};

#pragma once
#include <glew.h>
#define GLFW_INCLUDE_GLU
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include "GlslShader.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtx/transform.hpp>
 
#include "SimpleCamera.h"
#include "skybox.h"
using namespace std;
using namespace glm;
 
 
class App
{
public:
    void setup(int w, int h, string captionWindow, bool useAntialising);
    void update();
    void draw();
    void exit();
    void setupScene();
 
    static void error_callback(int error, const char* description);
    static void key_callback(GLFWwindow *window, int key, int scancode, int action, int mods);
    static void mouse_callback(GLFWwindow *window, int a, int b, int c);
 
    static App& getInstance() {
        static App app;
        return app;
    }
 
    GLFWwindow *getWindow() {
        return window;
    }
 
    vec3 modelPos;
    vec3 modelScale;
    vec3 angles;
 
    GLuint textures1;
    GLuint textures2;
    SkyBox skybox;
    
 
private:
    GLFWwindow *window;
    float mixFactor;
    SimpleCamera camera;
};