Hey there, I totally get how frustrating it is when an install hangs right before the finish line—especially after swapping in a new SSD and going through the hassle of network recovery. Let’s break down the fixes for your issue, starting with a critical note first:

You mentioned formatting to "AFP2"—that’s likely a mix-up! AFP is a file sharing protocol, not a disk format. For macOS Sierra (especially on a 2012 MBP), you need to format your SSD to Mac OS Extended (Journaled) (with a GUID Partition Table) for reliable installation. That’s probably one of the root causes here.

Here’s your step-by-step troubleshooting plan:

• Reformat your SSD correctly
  Boot back into Recovery Mode (Cmd+R), open Disk Utility:

  1. Select your SSD’s main volume (not the physical disk itself) from the sidebar.
  2. Click "Erase", set:
     • Name: Something simple (e.g., "Macintosh HD")
     • Format: Mac OS Extended (Journaled)
     • Scheme: GUID Partition Table
  3. Wait for the erase to finish, then quit Disk Utility and retry the install.

• Reset NVRAM/PRAM
  Old Macs often have cached settings that mess with installations:

  1. Shut down your MBP completely.
  2. Turn it on, immediately hold Option + Cmd + P + R until you hear the startup chime twice.
  3. Release the keys, let it boot back into Recovery Mode, and try the install again.

• Ditch network recovery—use a USB install drive
  Network installs are prone to corrupted downloads, especially if your connection drops even briefly. Here’s how to make a bootable drive (use another Mac if you have one):

  1. Download the full macOS Sierra installer (version 10.12.6) using Terminal on the other Mac:

     softwareupdate --fetch-full-installer --full-installer-version 10.12.6
     

  2. Format an 8GB+ USB drive to Mac OS Extended (Journaled) (name it "SierraInstall") via Disk Utility.
  3. Run this Terminal command to create the bootable drive (replace paths if needed):

     sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/SierraInstall --applicationpath /Applications/Install\ macOS\ Sierra.app --nointeraction
     

  4. Plug the USB drive into your 2012 MBP, boot holding Option, select the USB drive, and run the install from there.

• Run Disk Utility First Aid
  Even a new SSD might have minor partition issues:

  1. In Recovery Mode, open Disk Utility.
  2. Select your physical SSD from the sidebar, click "First Aid", then "Run".
  3. Repeat this for the volume on the SSD too. Fix any errors before retrying the install.

• Check the install log for clues
  When the install hangs, press Cmd + L to pull up the installation log. Look at the last few lines—they’ll often tell you exactly which file is corrupted or failing to open, which can point you to a specific fix (like re-downloading that component or adjusting disk settings).

Give these steps a try, starting with reformatting to the correct disk format—it’s the most likely fix here.

内容的提问来源于stack exchange，提问作者JMBruno