Hi Patrick. Thanks for both replies, and yes - both pieces of kit were showing as red in their titles. I only had the REL1000_0 working/responsive without anything connected for a couple of minutes.
Then, if I recall, I opted to upgrade the firmware. After that, it’s been unresponsive other than appearing in the panel and flashing on and off, with no further clickable options. I’ve now tried it with three laptops and three different 12v 2A power supplies.