Tag Function Stopped working

Hello.

For some reason when I try to use the_tags anywhere my site will not show the tags, I have a tag cloud and that works etc ….

Here is the code

<?php
     the_tags('<ul><li>','</li><li>','</li></ul>');
?>

I am lost here, I have been working with wordpress for a while and I am not totally green …

What could I be missing here?

Any help at all would be great!