Main class not found in IntelliJ although project was fine recently

I have a project that was working fine until recently. Suddenly, I am getting the error message "Main class not found". Attempts to fix the issue using the configuration dialog have been unsuccessful. Even navigating to the exact file that contains the main class does not work. I attach three images: the Edit Configuration dialog, the top half and bottom half of the Project panel. The correct class that contains the main() method is ReversiGUI.