Ok so I have an older MacBook Pro and I have a SSD drive that I know works great as a external but when I put it in my laptop as the internal drive it is not available when I put my OS disk in. I don't get it. I've tried formatting it and I've tried other drives in the same laptop and they will work. Like I said, I can take it out and plug it in as an external and it works fine. I'm so confused. Can anyone help?
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