It may well be the WiFi card has decided it is not going to work any longer. It happens. I would suggest trying the information below, and if that doesn't help, see if you can connect via Ethernet cord. If you can, then you will need to either connect that way, get the internal WiFi components replaced, or get an external WiFi card that would plug into your USB port.
When WiFi won't connect.
First, make sure your laptop is 'not' connected to the modem/router via an Ethernet cable and follow the steps:
1. Go to "Control Panel".
2. Next go to "Network and Internet" and then "Network and Sharing".
3. Now click on "Manage Wireless Networks".
4. On this screen, remove all wireless connections by "right clicking" on it and select "Remove network" from the drop down menu.
5. After doing this, close the windows and scan for the "Wi-Fi networks".
6. Click on the available network that you want to access and select "connect".
7. It takes a moment, but then you will be asked to give a password for your Wi-Fi connection. Type in the password and click the "connect" button.
It should now be connected.
NOTE: If this doesn't work, you may want to reset your modem/router, and then once it is fully loaded again, repeat the above steps.