I rec'd a new MegaSD today, January 9 2020, from StoneAgeGamer.
I went to the Firmware Update/Register product page: https://downloads.terraonion.com/user-registration
The Serial Number on the sticker inside my cartridge gives me the error:
*The product serial number does not exist.*
I've seen other people on this forum get the same error resolved.
Please reach out for next steps.