Now High Sierra can't find my SSD startup disk...but booting externally

[lindyman77]

Super weird issue going on. Upgraded my 13" 2011 MBP with a Samsung 840 Pro SSD to High Sierra. (Automatically upgraded to APFS with TRIM enabled) Last night it wouldn't boot showing only a flashing folder/question mark. Did all of the usual stuff PRAM, Recovery Mode, repaired permissions, etc. Nothing worked; it just won't boot.

Took the drive out of the machine and put it into a USB enclosure to see if it would boot externally and it does! I have verified that there is nothing wrong with the drive. I can boot it when it is attached to the machine externally and use it as normal. I can even make it the startup disk when external and it works flawlessly.

As SOON as I put it back into the machine, the computer says it can't find the startup disk. Has anyone ever come across this before or seen similar behavior with 3rd party SSD's??

 

[ljonesj]

Sounds like the hd cable inside the machine is bad either not connected or just plan bad

 

[Fishrrman]

I agree with the post above.
Could be the ribbon cable wearing out.
It's a cheap and easy fix.
Go to ifixit.com to see what's involved. You can order the replacement cable from them, or find it online.
BE SURE TO BUY AND USE THE RIGHT TOOLS.
(I think you need a Phillips #00 driver and a TORX T-6 driver)

 

[green86]

I agree with the post above.
Could be the ribbon cable wearing out.
It's a cheap and easy fix.
Go to ifixit.com to see what's involved. You can order the replacement cable from them, or find it online.
BE SURE TO BUY AND USE THE RIGHT TOOLS.
(I think you need a Phillips #00 driver and a TORX T-6 driver)

I see this problem multiple times a day. I agree, it is the cable.

 

[lindyman77]

Thanks all. I've tested this by putting in an older spinning media drive and was able to boot just fine??

 

[ljonesj]

Could still be the cable some stuff is just finicky with stuff my 09 Mac mini would on any laptop ddr3 were my MacBook Pro mid 2010 would through a fit if any thing but a matched pair of mush kin was put in did not matter if it was junk in matched or Samsung it had to be mushkin