Many things can make this happen, we will list a you the most common, problems.

A. You wireless device was not installed properly or the driver is corrupted.

1. Go to your device manufacturer's website and download the latest driver available.
2. Uninstall the old driver.
3. Install the new driver.

B. Your network is not properly configured.

1. If your network is set to DHCP then be sure that your network card is set to automatically.
2. If your network connection has a static ip then you must contact the person that created your network(or your Internet Service Provider) to give you your IP's.

C. Your network card is damaged, or it's not functioning properly.

1. Contact the store you bought your laptop from.