A customer of mine failed to update to Sonoma (or so it seems). Now the Mac does not boot.
I have removed the screen and have access to the status lights. The first LED on its own lights up, followed by 2 and 3 (1st 2 of the bank of 4). they then go off in reverse order and repeat.
This is without touching the power button and indeed even after I disconnected the button.
Any ideas as to where to start would be appreciated.