Please help resolve the problem.
I have a project in Wordpress. The problem is that JPG thumbnails are not generated out of the files uploaded to media library. There is the proper snippet in the [login to view URL] file:
add_theme_support( 'post-thumbnails' );
add_image_size( 'xxs_size', 100, 100);
add_image_size( 'sm_size', 300, 300);
Although it generates PNG thumbnails, JPGs are not generated. When I run Regenerate thumbnail plugin, I get "ERROR: File is not an image."