Map will not show on category archive

I cannot seem to get the map to display all markers for all posts in each category.
I am using this code:

<?php
 if (is_category()) {
  $category = get_query_var('cat');
  if (class_exists('Geotag')) {
   Geotag::the_geotag('print_map', array('marker_query' => 'cat='.$category));
   }
 }
?>

The map is just not showing?
The map is showing on individual posts when I include the shortcode [gmap].

Ideally, I want to add:

– one map on my homepage showing all of the tagged posts.
– maps on category archives showing all of the posts tagged in that category