FIX: [STUDIO-1615] adjust message for project save failed

Change-Id: Ia135053dd2206ffb2c743df65ea5273cb95f7666

src/slic3r/GUI/Plater.cpp

@@ -7423,7 +7423,7 @@ int Plater::save_project(bool saveAs)
 
     //BBS export 3mf without gcode
     if (export_3mf(into_path(filename), SaveStrategy::SplitModel) < 0) {
-        MessageDialog(this, _L("Failed to save the project.\nPlease check whether the project file is opened by other programs."), 
+        MessageDialog(this, _L("Failed to save the project.\nPlease check whether the folder exists online or if other programs open the project file."), 
             _L("Save project"), wxOK | wxICON_WARNING).ShowModal();
         return wxID_CANCEL;
     }