I'm repairing a 13" MacBook Pro Early 2011 (A1278). This will seem like a duplicate issue, but stick with me and you'll see something odd is going on.
TDLR; Fixed missing/undetected boot drive issue with new SSD and SATA cable, or so I thought. The issue still persists, but I've discovered it only happens when the MacBook Pro is left shut off for more than ~5 minutes! If I shutdown, then reboot within a few seconds or 2-3 minutes it works. If I leave it much longer the boot fails with the folder and question mark icon!
This MacBook Pro has the "question mark on folder" boot issue – here's a picture. This usually indicates a corrupt/failed boot drive or faulty SATA cable. I had the same issue on my own 2012 MacBook Pro a few years ago, and did the same repair (replace the cable and SSD upgrade) so I thought it would be easy.
The repair went smoothly. I got High Sierra installed on the new SSD by creating a bootable USB. Rebooted a few times afterwards to confirm all was well and considered it a job well done.
Unfortunately, when I tried to boot the MacBook Pro later in the day it displayed the error again on boot! I performed an SMC and PRAM reset and then it booted up. I assumed all was well.
I decided to verify my work a little later, and it failed to boot again!
It seems as though the issue occurs if the MacBook is left sitting without power for a while. If I leave it sit on the boot failure screen for a few minutes, then reboot, all is fine. I assume the original issue was never the old HDD or SATA cable, but something power related maybe?
I appreciate any ideas you have.
Best Answer
This sounds like a failing NVRAM (Non-Volatile Random Access Memory) chip - it's not holding the boot values.
When you do an NVRAM reset, it clears the pre-boot environment forcing your Mac to search for bootable volumes which it then writes to NVRAM. After you shut it off, power is removed from the NVRAM chip and as the voltage dissipates, it loses or corrupts the contents of it's memory. It could be the chip itself or the associated circuitry that supports it - without putting hands on, it's impossible to know.
You have to take it in for service. There are board level repair shops that can replace the actual chip(s), or you may need to replace the entire logic board.