Comments title won't localize on my custom theme

I have copied the title from twentyleven, replaced the text domain with my own and nothing is happening. The .po generator does not recognise this and therefore I cannot translate it.

<?php
				printf( _n( 'One thought on &ldquo;%2$s&rdquo;', '%1$s thoughts on &ldquo;%2$s&rdquo;', get_comments_number(), 'gpk2' ),
					number_format_i18n( get_comments_number() ), '<span>' . get_the_title() . '</span>' );
			?>

I’m wondering if I’m missing something fairly obvious. Thank you.