prlsrvctl fails for remote machines - login failed: Unable to connect to Parallels...

I'm trying to perform some automation of my VMs, via prlsrvctl and prlctl. I have two computers, both with Parallels Desktop installed. On both computers, I can run "prlsrvctl info" to get a basic dump of the product's configuration. When I try to issue the same command from one machine to the other, via:

prlsrvctl info -l usernameassword@hostname

I always get the following error:

Login failed: Unable to connect to Parallels Service. Make sure that the prl_disp_service process is active and it is not blocked by Firewall. For details, please refer to http://kb.parallels.com/en/8089. If the problem persists, contact the Parallels support team for assistance.

This happens regardless of which machine originates the request and which machine is the target. Thing is, prl_disp_service is running on both computers, and I have no firewall enabled, which makes the KB article referenced in the error message useless. In fact, trying to restart the launchdaemon via the commands recommended in that article yields:

hostname:~ username$ sudo launchctl stop com.parallels.desktop.launchdaemon
launchctl stop error: No such process
hostname:~ username$ sudo launchctl start com.parallels.desktop.launchdaemon
launchctl start error: No such process

How can I get prlsrvctl to talk to another machine?

 

I'm using SSH with public key authentication in the meantime.