Have you tried deleting and re-creating a new wifi connection?
System Preferences>Network, select the Wifi network on the left and click on the 'minus' key to delete it (you may need to input your admin password to allow this). Apply the changes.
Still in Network Preferences, click on the 'plus' sign to add a new network, select Wifi and let it create a new network. Try re-connecting your computer to this new network.
If that doesn't help, try creating a 'new location':