sophos support
Why won't Sophos open on my Mac Mini?
Mac mini (Late 2012), OS X Yosemite (10.10.5)
Why won't Sophos open on my Mac Mini?
Mac mini (Late 2012), OS X Yosemite (10.10.5)
You don't want Sophos on your Mac. It is worthless scamware. It offers no protection and only causes problems. I strongly recommended that you uninstall it.
It's been doing a great job until just now when I found it wouldn't open..How do I uninstall it?
Follow the directions at https://community.sophos.com/kb/en-US/120838
Since there are no virus on the Mac, there is noting for it to do beside use resources on your Mac and cause troubles. So I am completely baffled by your comment of it doing a great job.
sophos support