Laptop will not power on

When I press the power button, the keyboard backlight flashes briefly, then nothing. Same with power supply attached / battery only.

I’ve tried the “disconnect battery, press power button 10 times at 1 second intervals, then hold 30 seconds, reconnect battery, attach to AC power, power on” sequence, and that doesn’t work either.

There was no precipitating event. I didn’t drop it, or spill something on it. It just stopped powering on one day.

Does anyone have another repair pathway? If you’ve fixed this problem, please let me know how!