When using packages form repo.zabbix.com on Debian 8.6 and Ubuntu 16.04, after installation and rebooting server zabbix_agent or zabbix_server don't run. This systems use systemd to start processes, so the easiest and correct fix is to use command:
systemctl enable zabbix-server
systemctl enable zabbix-agent

Solution described also https://www.zabbix.com/forum/showthread.php?p=188380, still not fixed.

How to reproduce problem:
1. Instal/configure repo as described on Debian 8, Ubuntu 16.04 or later: https://www.zabbix.com/documentation/3.0/manual/installation/install_from_packages/repository_installation#for_debianubuntu
2. Install zabbix-agent (or zabbix_server), current LTS version 3.0.5
3. Reboot system
4. Zabbix_agent (or zabbix_server) should work, but is not.