Erasing disk and reinstalling MacOS

There may be a matter of choosing a partition; or if you erased

that too, a fuller re-install from online utilities may be necessary.

Further instructions should be within the companion article cited.

While there are some features and noted instructions in another reference:

• What to do before you sell, give away, or trade in your Mac - Apple Support

//support.apple.com/en-us/HT201065

Ones linked in my reply cover your instance, and then some.

When you erased the drive ~ you might have gone too far.

Or maybe not far enough..!😸

How to reinstall macOS

Follow these guidelines during installation:

• If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
• If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
• If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.

To be clear- when you boot into recoveryOS (Holding CMD + R on startup) and click "Disk Utility" from the four options, does your disk appear there?

If it appears in Disk Utility but cannot reinstall macOS on the disk, ensure you followed the reformatting instructions under 'Use Disk Utility to erase your Mac' - Use Disk Utility to erase an Intel-based Mac - Apple Support

If it doesn't appear in Disk Utility, your Mac needs service. You'll have to contact Apple Support.