I wiped both of my SSD and HDD in Recovery Mode on my Mac Mini 2012. Then I went to reinstall macOS on my SSD, but it didn’t show up in Disk Utility. My HDD still shows up though. The funny thing is, my SSD appears when I run “diskutil list” in Terminal. How come it’s detected in Terminal but not in Disk Utility?
Do you have a Fusion Drive?
If you somehow created a Fusion Drive with your HDD and SSD, Disk Utility will only show one drive. But Terminal will show you all the drive.
You can split the Fusion Drive to fix the issue.