Davidfor, you are indeed a Grand Sorcerer. Thanks again for the advice. I was able to get this device up and running again.
Strangely enough, I could not get the factory image to work. I've tried 2 different microSD cards, both 4Gb, and neither was accepted by the device. When I tried to boot with those cards, the red power light lit up briefly, then went out and the screen just stayed blank. I ended up triple-checking the model ereader that I was working with, but it is indeed a Glo HD.
I wrote the SD card image using a tool called USB Image Tool.
Source:
https://www.alexpage.de/usb-image-tool/
Using another tool called Mini Partition Wizard I was able to see that the SD card had the different partitions I was expecting, leading me to believe that it was written correctly.
For reference, this is what my original SD card looked like, partition-wise
I'm not sure why it wouldn't accept the SD card built from the factory image.
I had also previously tried the factory reset using the pinhole button, but where you're supposed to boot to a screen with square icons, mine just stayed black after showing those initial round loading dots. In the end I was able to do the reset by keeping the power button pressed and repeatedly tapping the bottom corners of the screen and then releasing the power button when the screen changes. It took a few tries to get the timing right, because the first few times I tried it, the screen just stayed black. But after one last desperate attempt, an actual factory reset was triggered and I'm able to configure my reader again.
A massive THANK YOU for your help. Now we can have ebook Christmas gifts again
