Continued from my previous reply.
tim_mia Said:
"Need help reinstalling MacOS: Thank you for replying! The dulled-out Mount button for the top "APPLE SSD AP02" is actually not click-able, only the "Macintosh HD" below it can be clicked/changed, and it was already mounted when I tried to install the system"
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Installing the MacOS on an Empty Drive:
Incompatibility may be the issue here. If so, then that is because your Mac does not have the hardware to go past a certain macOS.
I. Determine which macOS(s) can be Installed:
A. Start Here: Learn About Compatibility and how to Identify your Specific Mac Model - Apple Support
B. How to Verify:
I. Reveal your Model:
What is the Model of your Mac? To find out...
- Go to: Apple menu
- Click: About this Mac
- View: Second Line-Down
then...
II. Compare the Results:
See if the Model you found is shown here:
then...
III. Perform the Install:
A. First, Back Up your Mac First: Be certain you Create a Time Machine Backup of your Mac, so that way you can have something to restore your Mac from, should anything go wrong with the reconfiguration.
B. Finally, Install the MacOS:
- Use WiFi or Ethernet: You an use Ethernet or WiFi. Using a hardware connection(Ethernet) is usually more reliable than a wireless one(WiFi). Use this adapter, if you have no Ethernet connection: Apple USB Ethernet Adapter - Apple
- Use Internet Recovery Mode: Hold these three keys down upon boot: Option-Command-R
- Use a Bootable Installer: Go Here: Create a Bootable Installer for macOS - Apple Support. Using Terminal, you'd connect a USB Flash Drive, and then install it with the following command. You need a different Mac to create one --ask a friend or family member if you may use their Mac to create it.