Ошибка в DLL

    const void RenderMain(Render& render) {
         render.clearRenderBuffer(); //clearRenderBuffer - неразрешенный внешний элемент
    }

#ifndef RENDER_HPP
#define RENDER_HPP
 
#include "SFML\Graphics\Drawable.hpp"
#include "SFML\Graphics\Shader.hpp"
#include "SFML\Graphics\RenderTarget.hpp"
#include <map>
 
class Render {
    std::map <sf::Drawable*, sf::Shader*>   renderMap;
protected:
    Render(void);
 
    ~Render(void);
 
    const void render(sf::RenderTarget& _target) const;
public:
    const void appendPair(sf::Drawable* _drawable, sf::Shader* _shader = nullptr);
 
    const void popPair(sf::Drawable& _key);
 
    const void replacePair(sf::Drawable& _key, sf::Shader* _newValue);
 
    const void clearRenderBuffer(void);
};
 
#endif //!RENDER_HPP

#include "Render.hpp"
 
Render::Render(void) {}
 
Render::~Render(void) {}
 
const void Render::appendPair(sf::Drawable* _drawable, sf::Shader* _shader) {
    renderMap.insert(std::pair<sf::Drawable*, sf::Shader*>(_drawable, _shader));
}
 
const void Render::popPair(sf::Drawable& _key) {
    renderMap.erase(&_key);
}
 
const void Render::replacePair(sf::Drawable& _key, sf::Shader* _newValue) {
    renderMap.erase(&_key);
    appendPair(&_key, _newValue);
}
 
const void Render::render(sf::RenderTarget& _target) const {
    for (auto iterator = renderMap.begin(); iterator != renderMap.end(); iterator++)
        _target.draw(*iterator->first, iterator->second);
}
 
const void Render::clearRenderBuffer(void) {
    renderMap.clear();
}