1 have you got now or had before Mcafee installed another AV scanner installed on this PC? If so you need to have run the AV's own removal tool; preferably before McAfee was installed.
2.Have you rebooted since it happened ie did it happen after an update see below.....
3. Try removing Mcafee completely as per the below link and reinstall after rebooting.
4. If above no use try running the Virtual technician program and note the session number and call support if the technician program and the above suggestions fail to help you.
I would run No 4 if 1 above does not first apply.
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