I have a 2015 MacBook Air 13 running macOS Sierra. I got it without a working internal SSD. Now it only runs on an external SSD via USB cable. I would like to upgrade to High Sierra, but an error prevents me from doing so.
The SSD is split into 2 partitions:
1 partition is in APFS format, and when I try to install on it I get an error that I need macOS Journaled format.
The 2nd partition is in macOS Journaled format, and when I try to install to it I get an error: "You may not install to this volume because the computer is missing a firmware partition".
In recovery mode, I am prompted to install macOS El Capitan. I have tried so many methods from the internet, but have not found a solution.
The purpose of my upgrade to at least 10.13 is to support NVMe. I bought an m2 SSD, and an adapter to connect the SSD (Apple has its own connector for m2 SSD, which is different from the usual PCI-E). Now my MacBook can't see the internal SSD. Maybe if someone knows how to solve the problem differently, I won't need to upgrade to High Sierra.
Thanks a lot in advance for any help!
