[Plugin: WP-PageNavi] Code for single post pages?

Using WP-Pagenavi 2.61 on WP 2.9.2. The plugin works on my index and category pages. But when I try to insert the code <?php wp_pagenavi(); ?> into the Single Post template (single.php) the pages do not appear. My template is WP-Pagenavi ready, so should I be adding a different code, or does this plugin only work on index and category pages, not single post pages?

https://www.ads-software.com/extend/plugins/wp-pagenavi/