Gravatar not showing up.

I’ve been reading and re-reading all the support listed about Gravatars and have tried every suggestion listed and triple-checked my code. I’m using the official gravatar plugin, i’ve activated it and have this code:

<img src=”<?php gravatar(); ?>” alt=”gravatar” />

..inserted just above:

<?php comment_text() ?>

Currently nothing is showing up. If I add align=”left” then a small indentation on the left appears where it should show up. If I add in the parameter for a default image that’s hosted on my server, that shows up. But never an actual Gravatar or the Gravatar default image. What am I doing wrong?! Any ideas welcome!