[Plugin: WordPress Posts Timeline] css not working

Hi
Thanks for the plugin. It is exactly what I need for my site.
I would like the timeline to be on a category page so I’ve
included it in the category.php like this

<?php echo do_shortcode(‘[wp-timeline]’); ?>

My problem now is that the posts line up under each other and the line and circles are missing.
I can solve the problem by creating a post for the category page and including [wp-timeline]. Then it will show correctly on the post and also suddenly on the category page. But I don’t want this extra post.

I can’t understand why this happens, so any help would be greatly appreciated.
Thanks
Ellen

http://wordpress.org/extend/plugins/wordpress-posts-timeline/