Prev/Next not showing up

Hello hiys, I am having weird issues with a theme I am developing… first, I couldnt see any post if I didn’t add

<?php query_posts('post_type=post') ?>

before the loop. Can’t see any reason for that, as the issue persisted even when switching theme O___o

then, i couldnt call the prev/next page code

this one didnt work:

<?php posts_nav_link() ?>

yet this one did:

<?php previous_post_link(); ?> | <?php next_post_link(); ?>

Why does my WordPress think I am on a single page?
Any help?
Thx!