Permission problem with FreePBX
Freepbx cannot write some files in /etc/asterisk, they need different ownership:
dcerouter_102263:/etc/asterisk# chown www-data sip_additional.conf
dcerouter_102263:/etc/asterisk# chown www-data sip_registrations.conf
dcerouter_102263:/etc/asterisk# chown www-data iax_additional.conf
dcerouter_102263:/etc/asterisk# chown www-data iax_registrations.conf
dcerouter_102263:/etc/asterisk# chown www-data zapata_additional.conf
dcerouter_102263:/etc/asterisk# chown www-data queues_additional.conf