ENH:rry again after subscription failure

Change-Id: Ieedc4059834561ed77f2e66dbf93be21a2d62b61

src/slic3r/GUI/GUI_App.hpp

@@ -297,6 +297,8 @@ private:
 
     boost::thread    m_check_network_thread;
 public:
+    //try again when subscription fails
+    void            on_start_subscribe_again(std::string dev_id);
     void            check_filaments_in_blacklist(std::string tag_supplier, std::string tag_material, bool& in_blacklist, std::string& action, std::string& info);
     std::string     get_local_models_path();
     bool            OnInit() override;