All over again... suddenly the McAfee Security Center ckaims it needs activating but the button doesn't work.. just like before https://community.mcafee.com/thread/40133 !
Why can't you produce a product that keeps on working!??
Is that from the interface or by right-click - "Verify subscription" or both?
Try this FAQ and if that doesn't help try the Subscription Repair Tool.
Failing that and as it's the weekend withy few people around, I suggest contacting Technical Support, it's free via phone or online chat, linked under Useful Links at the top of this page.
Have you been using either registry cleaners/optimizers and/or System Restore? This can sometimes happen with those.