The command to read the EZIO8SA revision level returned a 00, which is of course wrong. The Write command to Set the Configuration Register with the Broadcast Status Chg option was issued but had no affect because the following Read of the Configuration Register came back with no options set. The PLM was accepting commands from the powerline but either was not passing them to the EZIO8SA or the EZIO8SA was not responding. I get the same results if I unplug the cable between the PLM and the EZIO8SA so I cannot tell which device was not working correctly. With things working now one or the other was affected by the power fluctuation. Or perhaps the Cat5 cable came loose on one end or the other coincident with the power fluctuation. Once I had a cable come loose. Looked like it was connected correctly but the plastic locking tab had not clicked with that end of the cable was not making a good connection. It created a problem when I moved some cables around. Still looked like it was plugged in okay but when I pushed harder I heard the locking tab snap into position.
Whatever the cause, glad things are working again!