No language is selected in the languages property of the international script line.
The current script cannot be previewed or run until a language is set.
Solution
•Edit List of Languages: Q++Studio automatically opens up the Languages property editor.
•Use one of the preferred Languages: Lists the languages that you selected in international preferences.
•Select a Language: Opens up a pop-up menu containing all the languages contained in the shared Languages database.
Long-term solution
If you select a default language for new scripts, then this message will no longer appear when creating new scripts.
Topic 015030, last updated on 22-Mar-2021