Just delete file robots.txt. WordPress is generating virtual robots.txt file, and Yoast SEO plugin (and other plugins too) allows you to customize it. But, if you have an actual robots.txt file, it will prevent virtual one to work.
Just delete file robots.txt. WordPress is generating virtual robots.txt file, and Yoast SEO plugin (and other plugins too) allows you to customize it. But, if you have an actual robots.txt file, it will prevent virtual one to work.