Unable to Install OS/Unmountable SSD/Macbook Pro Mid 2012

Lee Polikoff wrote:

I have a mid 2012 Mackbook Pro. I had a 500GB WD Blue SSD working for the last few years. 2 days ago, when I booted I got the dreaded ? sign. I removed the disk and hooked it to another mac and was able to read the disk, and copy the data from it.

I put it back in and tried erasing and fixing the drive but it wouldn't mount. I removed it and hooked it to another computer and deleted all partitions, and I still couldn't get it to mount.

I took out an old disk based hard drive and was able to erase, mount, and install Catalina. So I figured there was something wrong with the SSD. So I got a crucial 500 GB and I am having the exact same issues. Unmountable after erasure. Unable to install any OS on it. I am at a loss as to what I need to do to get the SSDs to work again. HELP?

One point of failure on mid-2012 MBP was the SATA cable.

The SSD is more demanding then the slower mechanical HDD, and a classic symptom like yours.

SATA replacement 15" MBP mid-2012

https://eshop.macsales.com/item/Apple/9230084#15_inch

SATA replacement 13"MBP mid 2012

https://eshop.macsales.com/item/Apple/8211480/%20%2013%22%20MacBook%20Pro%20SATA

Lee Polikoff wrote:

Thanks, I'll give it a shot.

all new drives need to be formatted before use, yes

File system formats available in Disk Utility on Mac - Apple Support