Not using the MFP product I can only guess. Is the machine connected to the Internet and showing the right time and timezone for the system clock? That would be how it synchronizes these things I would imagine.
There's a FAQ on it here: How to set up McAfee Family Protection Time Limits
But as you are using Cox I guess you are in the US which has 24/7 free online phone (or chat) Technical Support, I would take advantage of that. Link below.
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