I just resolved a problem that was haunting my Mac Mini and wanted to share. For some reason, my Mac Mini would be unable to connect to the wireless router in my home --- I followed a YouTube video that suggested that I turn off Wifi and then completely shut down the Mac Mini and then even remove the power cord completely from the Mac Mini. After waiting a bit, I would restart the Mac Mini and it seemed to work, but only sometimes. This was happening all to often and was not a reasonable solution.
Finally, I went into the Uverse router configuration using another computer that was not having difficulties with connecting to wireless. It turns out that BOTH the 2.4GHz and 5GHz radios were configured with the same SSID name. I changed the 2.4GHz name and restarted the Uverse router. Now, I am no longer having issues with my Mac Mini connecting to the router and it even is able to use the 5GHz frequency.
It was painful, but I think that this solution works. I hope this helps someone else avoid the pain that I experienced.
Mac mini, OS X El Capitan (10.11.3)
