If something is wrong with jmx settings jmx network interface goes to error state and never resolves (even the cause was fixed).
restarting java_gateway, zabbix server, switching host into unmonitored and monitored state.

the only helpful thing is remove host and add it again.

How to reproduce:
setup java with password (or ssl) protected jmx, set wrong password in web interface or ssl settings in java_gateway's startup.sh
after jmx network interface will switch into error state fix settings.
interface will stay in error state