Connecting Across a Subpanel


I am trying to connect livewires across a subpanel at a residence.  It has worked in the past, but more often than not the devices cannot find each other and establish a connection.  Is there a troubleshooting guide or a set up method that help me set up a reliable connection using this devices?  Any insight would be great.

Thank you,


Any guide for HomePlug AV devices on Google should do since they all work the same, have you had any luck with this?