Close registration for a course

You’d need to code that using the sensei_display_start_course_form filter. Something like this:

function display_start_course_form( $should_display, $course_id ) {
	if ( $course_id === 9999 ) {
		return false;
	}
}
function lock_course() {
	add_filter( 'sensei_display_start_course_form', 'display_start_course_form', 10, 2 );
}
add_action( 'init', 'lock_course', 11 );

Note that in Sensei 3.0, sensei_display_start_course_form will be deprecated in favour of sensei_can_user_manually_enrol so you’ll want to update that after updating.

And how can I do this for a specific course?

I tried to report $course_id but I didn’t get it.

Thank you!