Did Sierra's latest security update brick my device? I have an mbp mid-2012 running the latest Sierra. I installed the latest update which attempted to restart the machine. The usual progress bar was showing and then it shut off. Curiously, it didn't restart.
Now, when i press the power button, the sleep led flickers and then dies along with the machine. The screen never turns on.

Things I've tried


resetting SMC


Are these symptoms familiar to anyone?
The number of times the sleep light flashed was an indicator of the problem. Three flashes means the Mac can't find any RAM.

Practically, this means the RAM you have installed is bad, or has a bad connection. Step one is re-seat like you did. Meaning remove and reinstall the RAM. If you still have problems, swap it out with some other compatible RAM and see what happens.