Custom XBlocks are not allowed by default, you need to update settings.
Like all platform settings, you can either write inside /edx/app/edx_ansible/server-vars.yml and update the platform to generate the custom settings files.
Server-vars file is optional for edX installation since it contains your private installation settings (passwords, etc). You may add it yourself, a good example is given by Trinh Nguen: http://www.dangtrinh.com/2014/05/edx-platform-server-varsyaml-variables.html
Liubov
Settings -> Advanced Settings -> advanced_modules -> ["problem-builder"].To view this discussion on the web visit https://groups.google.com/d/msgid/openedx-ops/eecc5017-8ac7-4fb0-8c75-07f8349f84c8%40googlegroups.com.
cd /edx/app/edxapp
sudo -u edxapp git clone https://github.com/open-craft/problem-builder.git
sudo -u edxapp /edx/bin/pip.edxapp install problem-builder/
sudo rm -r problem-buildersudo /edx/bin/supervisorctl restart edxapp:*
sudo su edxapp -s /bin/bash
cd ~
source edxapp_env
python /edx/app/edxapp/edx-platform/manage.py cms syncdb --migrate --settings=aws
python /edx/app/edxapp/edx-platform/manage.py lms syncdb --migrate --settings=aws
sudo /edx/bin/supervisorctl restart edxapp:sudo /edx/bin/supervisorctl restart edxapp_worker: