So all of a sudden, after a week of using it, I get an error message on my zabbix server gui (http://localhost/zabbix/.)
zabbix server
The error says: Zabbix serve
Zabbix serve
Never had the problem until it suddenly appeared once, for me, the solution was to add (uncomment) the following line in /etc/zabbix/zabbix_server.conf
/etc/zabbix/zabbix_server.conf
ListenIP=0.0.0.0