iMac will not upgrade past Yosemite
I have a 27" mid-2015 iMac that I want to upgrade to Sierra. (That's as high as I can go and still use some legacy software I need for work.) I have downloaded the Sierra InstallOS.dmg package, run the installation, and get the message "The software was successfully installed."
However, when I reboot, I check "About This Mac" and it says I'm still running Yosemite. I repaired disk permissions, but that didn't help.
Any advice on how I can get Sierra to actually stick, and boot?
iMac Line (2012 and Later)