Erasing Macintosh HD problem
I want to erase my iMac (2010) disk running High Sierra as I am recycling my iMac. I followed the steps on "What to do before you sell, give away or trade in you Mac" published June 04, 2020. At step 7, erase your hard drive, after selecting the Macintosh HD in sidebar the Erase button will not highlight. Only First Aid and Partition buttons in tool bar are highlighted, Erase, Restore, Unmount buttons are not highlighted (made available).
iMac 27″, macOS 10.13