Document note not working on Packing-slip, but works on Invoice template

I am making a custom template for the packing slip. I want to add the custom invoice notes to the packing slips. But it’s not showing up.

This is the code. It works on Invoice. But not on packing slip. What should I do to have the code work on “packing’slip” too.

<div class="document-notes">
					<?php do_action( 'wpo_wcpdf_before_document_notes', $this->type, $this->order ); ?>
					<?php if ( $this->get_document_notes() ) : ?> <br>
						<h3><?php _e( 'Merchant Notes', 'woocommerce-pdf-invoices-packing-slips' ); ?></h3>
						<?php $this->document_notes(); ?>
					<?php endif; ?>
					<?php do_action( 'wpo_wcpdf_after_document_notes', $this->type, $this->order ); ?>
					<br>	

		<?php $this->document_notes(); ?>