How do you add in dynamic month and year in code snippets?

I’m trying to add in the dynamic month and year in my blog post titles, but it isn’t working.

This is the code I entered into Code Snippets. I’m using Rank Math as my SEO plugin. Is the code correct?

//* Shortcode to display the current month and year in WordPress
//* shortcode: [month_year]
add_shortcode( 'month_year' , 'current_month_year' );
function current_month_year() {
$year = date("Y");
$month = date("M");
return "$month, $year";
}
add_filter( ‘the_title’, ‘do_shortcode’ ); // activate shortcode in WP Title
add_filter( ‘rank_math/frontend/title’, ‘do_shortcode’ ); // activate shortcode in Rank Math Title
add_filter( ‘rank_math/frontend/description’, ‘do_shortcode’ ); //activate shortcode in Rank Math Meta Description

For my blog post title, I put “The Best XXX in [month_year]”, but the month and year doesn’t show up.

Currently I’ve removed the [month_year] from the blog post title since it’s not working.

The page I need help with: [log in to see the link]