I don't know much about the device and I haven't seen a firmware update file so far, plus I only own a Glo, so you'll have to help me here a litte to find out what the problem is
Do you already have shell access on your device?
Yes:- Does the file /tmp/invertScreen exist?
- Does the command "echo t > /tmp/invertScreen" trigger nightmode?
If so, the only problem is the new address of the LIGHT button. Please run the command: "hexdump /dev/input/event0", press the light-button twice and post the output.
No:- Install the debug version in the attachment
- Press the LIGHT button twice
- Connect to your PC
- Post the content of the file .kobo/screenInvertLog