[MGlitch]

Catalina seems to be a bit more sensitive about USB devices drawing power from the USB port. It -should- display a message in the top right about this.

For what it's worth I've used Catalina with a Forma, and with a Kobo Aura h2O original. While both devices came out after the Glo HD, the hardware involved should not have changed all that much. it's still connecting the internal drive to the Mac.

Have you tried connecting something else which would use data to the USB port in question, even a mouse or keyboard would do as they transmit to the Mac.

edit to add

Just updated to Catalina on my own iMac, I'd been holding off because the version of Photoshop I was using was still 32bit and I didn't really fancy getting into the terrible subscription service with Adobe but I found a viable alternative, anyway long story short my Forma shows up and loads in Calibre.

I'd test my Kobo Aura h2o but i really don't see the need as it'd loaded under Catalina on another Mac.

As the forums haven't seen any reports of this behavior under Catalina other than yours, I'd say it's specific to your hardware. Since the Kobo Glo HD mounts on another Mac, and you've tested the USB cable, I'd have to presume the USB port on your Mac has been damaged in some way.