I have the following two apps located in my virtualenv: backend backoffice.
The backoffice app has templates under:
backoffice/templates
So when I login into the Django shell, I can to do the following:
>>>from django.template.loaders.app_directories import Loader
>>> list(l.get_template_sources('index.html'))
[u'/var/www/venv2.7/lib/python2.7/site-packages/django/contrib/auth/templates/index.html', u'/var/www/venv2.7/lib/python2.7/site-packages/backoffice/templates/index.html', u'/var/www/venv2.7/lib/python2.7/site-packages/django/contrib/admin/templates/index.html']
So it seems the template is correctly found (l.load_template_source(('index.html') is also working). 
However, when I access my home page via the browser I get an error:
TemplateDoesNotExist at /
Can someone help me solve the puzzle? What am I missing?
update: full trackback
Request Method: GET
Request URL: http://192.168.211.140/
Django Version: 1.5.1
Python Version: 2.7.6
Installed Applications:
('django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.sites',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'backoffice',
 'backend',
 'django.contrib.admin')
Installed Middleware:
('django.middleware.common.CommonMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware')
Template Loader Error:
Django tried loading these templates, in this order:
Using loader django.template.loaders.filesystem.Loader:
Using loader django.template.loaders.app_directories.Loader:
/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/contrib/auth/templates/index.html (File does not exist)
/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/contrib/admin/templates/index.html (File does not exist)
Traceback:
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  115.                         response = callback(request, *callback_args, **callback_kwargs)
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/contrib/auth/decorators.py" in _wrapped_view
  25.                 return view_func(request, *args, **kwargs)
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/backoffice/views.py" in start_page
  177.     return render(request, 'index.html', context)
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/shortcuts/__init__.py" in render
  53.     return HttpResponse(loader.render_to_string(*args, **kwargs),
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/template/loader.py" in render_to_string
  170.         t = get_template(template_name)
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/template/loader.py" in get_template
  146.     template, origin = find_template(template_name)
File "/var/www/backoffice/venv2.7/lib/python2.7/site-packages/django/template/loader.py" in find_template
  139.     raise TemplateDoesNotExist(name)
Exception Type: TemplateDoesNotExist at /
Exception Value: index.html