Elasticsearch plugin turned red

Elastic Stack Kibana
1

Hello Bros'
In my setup here i suddenly found my setup stoped working with Elasticsearch plugin is red "Chaeck attachments", I have restarted the server several times but still not working.
Any help to have it back working would be appreciated. "I am network engineer, not a developer but I will do my best".

ELK
ELK1514×674 41.5 KB

Info:
Curator, version 5.4.1
kibana@5.6.16
logstash 5.6.16
Elasticsearch number" : 5.6.5"
lucene version lucene_version" : 6.6.1
ubuntu server 16.04

Thank you IA

2

5.6 is extremely old, EOL and no longer supported. Please upgrade.

3

Thank you for your replay, and according to my posted versions above, I need any resources that may help me through this process.
TIA

4

Any help in this reuired upgrade process.