Scan results say "no threats found" but immediately underneath says "issues detected"

The "Issues detected" message is usually safe to ignore. Generally this means the scanner came across compressed, corrupt or encrypted files. The video below will give you an in depth explanation of what this means and how to view the files that were detected.

But my log reads this:

Unable to initialize threat detection engine: virus data missing or unusable.

Scan stopped at 2015-06-24 13:41:22 -0400.

Hi Schweinghagen,

If you click the Sophos shield icon in the tray and select 'update now' does it complete? Once that's done you can try re-running the scan, and it should hopefully work. 

No. It updates it. But the Shield is grayed out and says On-Access Scanning Is Disabled. I can't seem to change that.

I upgraded to MacOSX 10.10.3 yesterday.

Hmm. Honestly, the easiest way to fix this is to uninstall SAV, restart your mac, and then reinstall it. 

Don't forget to use the 'Remove Sophos Antivirus' application, which you should have in Finder > Applications directory.

Sorry for the hassle, let me know if that doesn't fix it. 

Will give it a try and let you know.

Thanks for the help!

you're welcome!

Uninstalled. Reinstalled. Appears to be working perfectly.

Thanks again!

Perfect, glad you were able to get things up and running again!