Sorry I misunderstood, you ssh into the PC (which is actually a linux box) with the ip address 10.0.0.200, userid “hass”, then sudo poweroff. Mine is actually a PC but that’s a clever workaround and I can probably do something similar.
This is just an SSH, so you should be able to test it outside of HA, I have an SSH key installed as root, so I can do a shutdown using:
/usr/bin/ssh -i /home/david/.ssh/id_rsa root@desktop /usr/sbin/shutdown -h now
Where I am fully qualifying every path including the path to the private key that will authorize shutdown.
Note: SSH can be locked down so that a particular key can only run a single command - in this case shutdown - however I would suggest getting it working first then locking it down.