Ok. I launched license.exe, clicked "Activate online", new window asked for my Activation Key, found that in your email from back in early December (yes, off&on I've been at this that long), entered it, it filled in a new long string in the "Recovery Code" window, I clicked the "Recover" button, the printer woke up and the pc screen opened a new window that said to power off and back on the printer. Did that, the printer now seemed normal (no ERROR message). I opened the Maintenance menu on the printer, asked for a nozzle check and it printed that, saying the Firmware is 20.42.NW07K7 which is the XP-15000's correct chipless firmware.
So, I seem to be set. Thanks!