the_content() function not working for single event

Hello there,

I am using as reference the page https://webnus.net/dox/modern-events-calendar/overriding-mec-single-event-page/

Here is some code:

the_title();
the_excerpt();
the_content(); // Doesn't work

The first two functions work normally, but when I call the_content() function I get the following error:

Warning: count(): Parameter must be an array or an object that implements Countable in wp-includes/post-template.php on line 317

However, doing this works:

$content = get_post_field( 'post_content', get_the_ID() );
echo do_shortcode( $content );

This doesn’t make sense to me. Is this expected behavior?
I’m using PHP 7.4