We have a few esxi hosts monitored by Zabbix

All those hosts have a service configured based on availability

All was working fine until we rebooted 10 hosts

All hosts came up and all problems disappeared from problems section.

7 hosts got SLA calculated accordingly but 3 servers remained from the SLA perspective as down. they have 0% SLA

The services are all green.

There is no reason the SLA is 0.

It seems like there is a bug.

I have created a new service for the exactly same host and SLA is calculated correctly.