Apple - Get rid of "The Wi-Fi network ... could not be joined." message

  1. Go to Spotlight (magnifying glass in top corner) / Finder > Activity Monitor
  2. Search for SystemUIServer in CPU tab using the search bar located at top right corner
  3. Force quit it

try connecting after removing any USB device connected. It worked for me.

I followed many tips provided thru various Apple / Mac blogs. I did all of the obvious and logical tips, router, turn-off, turn-on WiFi and my MacBook Air wouldn't connect to my wireless network, or via a Bluetooth hotspot from my phone. It would connect on Bluetooth, even sending a pairing request only to disconnect. I could not load my Network name when choosing a network

So, I connected my iPhone (Did have an active connection to my wireless network) via USB as an option in my Network on the Mac. Then went to: System Preferences > Network. Under location, I went to Edit Location, created a location named "Untitled". Instead of Automatic, I chose "Untitled." I instantly received a password request for my network. I'm now connected and Location has defaulted to Automatic.Removed the iPhone connection and I'm up and running. It wasn't pretty, but it worked.