“Dates for Humans” and “Post Updated” plugins not working

This is so weird. I have WP 2.04 working just fine. Certain plugins work (such as “Hello Dolly” and “Auto Page Redirect” and “List Subpages”) but for the life of me, I cannot get any plugin to display the last time a particular page was updated.

The “Dates for Humans” and “Post Updated” plugins are listed in my Plugins page within wp-admin, and they are activated. Yet when I insert the particular code:

<?php v2_human_date([echo = true]); ?>

nothing comes up on my pages! What am I doing wrong? I can’t find anything obvious in the server logs.

Heeeelp!

Thanks so much,
Rick