Kibana show es cluster status red but es api show it as green

Why Kibana show elasticsearch cluster status as red but it shows green from es HTTP API?
It seemed that there is delay through the latter.

Kibana version: 5.5.2
Elasticsearch version: 5.5.2

Hi there, unfortunately 5.5 has passed its end of life date and we no longer offer support for it. Please upgrade to 6.3 or later to get support in the forums.

Thanks,
CJ