Addthis custom buttons not visible

Hello,
I wanted to use Addthis custom buttons in my posts, as I already do in my joomla articles.

I inserted the following code using a module in easyblog-after-content position

<div style="float:left; margin:-3px 20px 0px 0px">{modal index.php?option=com_content&view=article&id=44:iscriviti-alla-newsletter&catid=2&Itemid=182|title=Iscriviti agli aggiornamenti del blog|width=350|height=400}<button class="btn btn-large btn-info"><span class="fa fa-envelope"></span>Iscriviti agli aggiornamenti del blog</button>{/modal}</div>

<div class="addthis_sharing_toolbox visible-desktop" ></div>

<div class="clearfix"></div>

the above code displays a "subscribe to blog" button + the addthis share buttons.

The "subscribe to blog" button is showing, but the addthis share buttons are not (see attached image)

test here - scroll to the bottom of the article text

This same code is woking perfectly on my joomla articles: test here - scroll to the bottom of the article text

By inspecting the code, in the easyblog post the buttons seems to be there but somewhat hidden (the buttons images are not visible) - see attached image

Can you help me to sort this out?

Thank you