Symfony web debug toolbar does not show up

The toolbar inserts itself in pages by looking for a terminating tag on your generated page.

If you don't have a tag in your page the toolbar will not appear.

Add the body block to your template, so that the web debug toolbar would show:

# vim src/Acme/DemoBundle/Resources/views/Default/index.html.twig

{% extends '::base.html.twig' %}

{% block body %}
  Hello {{ name }}
{% endblock %}

Reference:

http://stackoverflow.com/questions/19147502/symfony-web-debug-tool-bar
http://blog.ijun.org/2015/06/symfony-toolbar-error-occurred-while.html