Problem: Previously working wireless network is not visible, nor can authorized wireless clients access after enabling time based MAC access control.
Product: Airport Extreme 802.11n
Setting Before Change (when working: Wireless network secured with WPA/WPA2 only.
Setting After Change: Wireless network security with WPA/WPA2 and Time Based MAC Address Access Control. I made the following changes in this order: 1. Changed MAC Address Access Control from Not Enabled to Time Access. 2. Changed (default) from Everyday All Day to None. 3. Added Wireless Client MAC Addresses assigning each Everyday All Day access. 4. Selected Updated and re-started base station.