If that combination does not work, unplug the PLM connected to the EZIO8SA, disconnect the cable to the EZIO8SA and plug the PLM back in. Then use the Utility to connect to the EZIO8SA with the EZIO8SA disconnected. The first command in that trace that is not getting a response is a Set MSB command which will be processed by the PLM without the EZIO8SA. Obviously the commands specific to the EZIO8SA will not work but the Set MSB must work as that is a PLM command, independent of the EZIO8SA. If the Set MSB does not get a response there is a comm problem between the PLMs.
Is there any other Insteon device that the Utility can access through the PLM without the passthru outlet? If so use the Manage Device Links tab and display a link record in some other Insteon device to confirm that PLM can communicate over the powerline.