Def Download Failed in PC Pitstop's Paid Products Posted August 29, 2018 · Report reply This has happened to me a few times after Windows10 updates. Turning the computer off and waiting several minutes has worked. Also going into your security settings and click on anti-virus and open supershield. Windows 10 then re-starts it. Make sure you have Windows Defender turned off. It does not like supershield. If all else fails, uninstall and go to PC website and re-install.