You make an error in the configuration of your Juniper SRX and vpn stops working and you get the error message:

error: the kmd instance kmd is not running

So you execute:

show system processes extensive | match kmd

and you get nothing but the prompt back. To fix

restart ipsec-key-management immediately

you will get the message:

error: IPSec Key Management daemon is not running

Then a few seconds later you will get the reply

IPSec Key Management daemon started, pid (some number)

Reference: https://kb.juniper.net/InfoCenter/index?page=content&id=KB10956