Calendar widget is not loaded

Hello,

I have added a calendar widget in the sidebar, using the Widget menu.
With other themes, the widget calendar is displayed, but it doesn’t show when using Ultra Theme.
Could you give a look please ?

Ultra Theme 1.0.2
Simple Calendar (Google calendar) 3.1.1

You can see the issue here :
http://www.amichien-miloup.fr/web/category/blog/

Code :

<div id="secondary" class="widget-area" role="complementary">
<aside id="gce_widget-4" class="widget widget_gce_widget"></aside></div><!-- #secondary -->

There is node code for calendar widget here.

It only happens with this calendar widget. Search widget can be displayed. There must be some incompatibility between the theme and the plugin. The code isn’t even loaded in the html.

Here is the beginning of the expected code :

<h2 class="widget-title">Calendar</h2><div class="simcal-calendar simcal-default-calendar simcal-default-calendar-grid simcal-default-calendar-light" data-calendar-id="43" data-timezone="Europe/Paris" data-offset="7200" data-week-start="1" data-calendar-start="1467151200" data-calendar-end="1467669659" data-events-first="1467280800" data-events-last="1467669659">
...

Have you had any issue like this before ?

Thanks for your help.