I'm trying to use server command /JHFORCEON from within livemap panel (External Command section).
Every time I'm trying to execute it, it says in the server log "parse error". Is there any way that I can reformat this command in order to be accepted?
Thanks!

Any slash-commands can't be used in the server console. They can be used from the client chat/console only.
I don't know of any server functions that would let you start or stop JH I'm afraid.