by ignotus » Mon Dec 16, 2019 10:55 am
It could be a number of reasons - wrong firmware file (wrong frequency), wrong settings in MIDI-OX, the new firmware defaulting to a contrast setting that prevents you from seeing the screen (after installing the firmware with MIDI-OX, is there any activity when you hit the pads?), faulty Atmega, faulty crystal... If it used to work and now it doesn't, it's obvious that something, somewhere, has changed. You still haven't said what firmware file you're trying to install.
If it ain't broken... fix it until it is.