If you decide to try this as-is, make sure that
the SW1 is ON (up) on the board. 

Much more importantly you must get the Apple ROM image into the
FLASH ROM. Easiest way to do it is by using the "control panel" 
application that comes with the board. Write the file "myflash.rom"
starting from address 0. This is an image taken from the AppleWin
emulator. Of course you can use some other image if you want. For
example use the old monitor instead of the Autostart.

KEY0 is the general reset that should bring back the MMC screen.
After you load a NIB image, press KEY3 - the 6502 reset.