My macbook air will not detect my home wifi anymore!

Question

In Summary:
Macbook air used to work perfectly on home wifi
Wifi dropped one day and all devises lost connection but when the wifi was fixed the MBA wouldn't detect it anymore even though all other devises did
MBA still works on all other wifi networks
How can I get my MBA to detect the home wifi again / why won't they link anymore?
My home wifi (Sky is the provider) dropped one day because the lines went down but after it was fixed the macbook air (2012) stopped detecting it..
The macbook will detect any other wifi network (office, public, friends houses etc) and works perfectly but will not even pick up the home wifi.
This is particularly confusing because all other devises including iphones, laptops, tablets etc will detect my home wifi without a problem.
The only time it has connected to the home wifi since dropping is when my laptop picked up my neighbour's wifi (which is rare where i live as houses are far apart) and then my home wifi showed up and worked perfectly until i closed the MBA and it wouldnt pick it up again
I have been without internet in my house for c. 6 weeks now even though the laptop appears to work ok on other networks and the home wifi works perfectly with other devices
Any suggestions would be much appreciated.

Answer 1

Go to System Preferences > Network. Select Wi-Fi or AirPort from the left column. Click the Advanced... button.
Under the Preferred Networks list, select every Wi-Fi network that appears, including the one(s) you want to use, and delete every one using the "–" (minus) button. Select the box "Remember networks this computer has joined" if it is not already selected.
OK then Apply.
Select your wireless network in your Mac's Wi-Fi menu and provide your wireless network password. Be sure the network you select is yours and not someone else's.