WIFI & extenders stopped working when the power went out.
Everything had been working fine. Then the city turned the power off for 3 hours for maintenance. Now my wifi and extenders no longer work.
iMac, OS X El Capitan (10.11), 16 GB of RAM
Have you tried an SMC reset?
Do Wifi still show in System Report or Network Pref Pane?
What does Network Diagnostics report?
Use Wireless Diagnostics to help you resolve Wi-Fi issues on your Mac - Apple Support