Yesterday WiFi was working!

You: When WiFi does not work and
 it was okay Yesterday!!!

Yesterday WiFi was working just fine in the office, I passed by the coffee shop and it worked perfectly there! Then I got home, no problem. Today I got to the office and I just don't understand what the issue is! I cannot connect to any network! its sooooo frustrating! You tried turning off the WiFi setting on your Mac and back on again and nothing works tried to forget the network or log in again it tries forever, gets on, then drops the connection or simply never connects!

Well for Mac users this can be a pain, and the most likely reason for this is the WiFi / Network preferences have become corrupted. I first experienced this after upgrading to Marverics OSX 10.9
and also encountered a similar problem on anther Mac on El Capitan OSX 10.11.x

For Mac users here is a workaround

1. Turn off your WiFi 
2. click on the Finder icon on your dock
3. Then hit Command+Shift+G
4. The go to folder command window [entry box] will appear
5. Copy or type this path below. [your may see this ~/Library/ delete and enter path shown below]
1. /Library/preferences/SystemConfiguration/
6. Hit return [enter] and you will see an window similar appear.
7. In this window create a folder Called OldWiFiPrefs [you may be required to authenticate this action]
   
8. Select the following files (as shown on the right->) and move them to your new folder:
1. [OldWiFiPrefs]apple.airport.preferences.plist
2. com.apple.wifi.message-tracer.plist
3. NetworkInterfaces.plist
4. preferences.plist
9. Now restart your Mac :)
10. Switch WiFi back on and log onto your WiFi hotspot[s] you may need to punch in the password again.

For windows users, if this happens on Windows 7 pro and above, you want to forget your network and try again, if this does not resolve the issue go to manage networks a list of all WiFi SSID's your computer "knows" are listed, delete the one you cannot connect to and then try re-connecting. you will be required to punch in the WiFi password again.

Happy Surfing!