zabbix remote hosts reporting data but availability unknown

[infusedhosting]

Hi all

Setup zabbix server and 2 remote servers so far. Looking to use zabbix to monitor a number of cpanel & directadmin hosts.
Ive installed the agent on 2 cpanel hosts, allowed the 2 ports through the firewall and added a couple of basic monitoring templates.
Both hosts are showing data in the dashboards for cpu, disk, network but both hosts availability shows unknown.

Any advice would be appreciated.

Thankyou

[Blevar]

How are your agents on host configured? Sharing config files would be helpful.

[troffasky]

If Zabbix agent is not new enough, in Active mode, Zabbix server will receive metrics but the Availability will just show as unknown.
I cannot remember which version is required to get a green light here.