Keep getting "<host> is not reachable" for "Template JMX Generic"

[scao]

Hey Guys,

I'm reaching a weird issues when linking template "Template JMX Generic".

Host is showing green "Z" in the configuration tab.

How to troubleshoot and fix the error?

Sample email notification:

Trigger: d2full04 is not reachable
Trigger status: PROBLEM
Trigger severity: Average
Trigger URL:

Item values:

1. jvm Uptime (d2full04:jmx["java.lang:type=Runtime",Uptime]): *UNKNOWN*
2. *UNKNOWN* (*UNKNOWN*:*UNKNOWN*): *UNKNOWN*
3. *UNKNOWN* (*UNKNOWN*:*UNKNOWN*): *UNKNOWN*

Original event ID: 1956

Thanks,
Shawn