glfw: glfwCreateWindow returns null

void Window::Create(std::string title) {
		glfwSetErrorCallback(error_callback);

		if (GL_TRUE != glfwInit()) {
			AC_CORE_ASSERT("Failed to initialize GLFW. This could be a problem with your hardware or software.");
		}
		else {
			window = glfwCreateWindow(500, 600, "Acorn Engine", nullptr, nullptr);
		}

		if (!window) {
			glfwTerminate();
			AC_CORE_ASSERT("GLFW failed to create the window.");
		}
		else {
			glfwMakeContextCurrent(window);
			AC_CORE_INFO("Successfully created GLFW window.");
		}
	}

Settings glfw hints don’t work. This code is in a dll. I am using a lib for glfw (glfw3_mt.lib)