Action center in Windows 8 says McAfee antivirus and spyware turned off. Going directly to the McAfee icon and opening shows an exclamation point and a note that real-time scanning is turned off. If I hit the button that says "turn on" then the items all go green like it has just made the changes. A few seconds later it returns the same message of "real time scanning is turned off". Something in McAfee is not running right. I have done the MVT and it says it corrected three problems, however the message and errors still exist unchanged. From Windows 8 action center I have also tried the button that says "turn on now" and it does nothing. The action center also has a view spyware button. It shows windows defender turned off and that McAfee is snoozed. Nothing within action center will turn it on.
Moved from Community Interface to VirusScan for better attention.
Windows Defender in Windows 8 should be off when another antivirus is installed.
Is your System Clock accurate both time and timezone-wise and have you tried updating McAfee?
If that doesn't help try running McAfee Virtual technician http://mvt.mcafee.com/ to see if it fixes things.
If not contact Technical Support via the link under Useful Links at the top of this page, it's free.