Chosen Solution
So I was gifted an old Mid 2010 MacBook Pro that at this point, I’m ready to just give up on. I purchased a Samsung 970 Evo 2.5 in. SATA SSD (250GB) and could not reinstall macOS no matter what I tried. I tried Internet Recovery, I tried using a USB installer and I continuously get the “prohibitory symbol” when it’s near completion of being installed. I’ve tried on both WiFi and Ethernet, same results. However, I can reinstall macOS if I throw in the original HDD but for obvious reasons. So I figured, let me see if the SSD is the issue and so I purchased a SATA to USB Cable and was able to successfully reinstall macOS onto that externally. Then I came across a thread on here that suggested upgrading the internal Hard Drive Cable, which I purchased and arrived today. I successfully installed it and once again tried to reinstall macOS to only get the same issue again! I can install macOS to the SSD if connected externally and can install it internally and it boot up fine but if I restart the computer it will boot to the “prohibitory symbol” It’s like it doesn’t like the SSD installed internally but will accept it externally? I don’t know what to do at this point. Anyone have suggestions or ideas? I’m beyond frustrated and usually can figure out these sort of things on my own but figured I would reach out for help on here. Thanks in advance to anyone who responds to this lengthy post.
Using the USB boot drive did you first format the drive fully to GUID Journaled file system? Are you using the correct OS version? The highest you can go to is macOS High Sierra (10.13.6)
