1. Check for any loose connections between the computer and the router.
2. Make sure the router is powered on.
3. Re-connect to the wireless network in Network settings.
4. Check if the correct wireless network is selected.
5. Power cycle your router and computer.
6. Disable the Firewall on your computer.
7. Restore the router to factory defaults.
8. Contact your Internet Service Provider (ISP) for further assistance.