Try connecting to the router with an ethernet cable between it and your laptop's networking port. If that works, check that you can detect your router's SSID (callsign) wirelessly -- if necessary moving the laptop into the same room as the router to test.
Then see if you can connect to the internet. If you can, the problem may be intermittent wireless signal and you should try to optimise your reception and avoid interference.
1) raise the router above furniture level
2) Experiment with channels (some will work better or worse depending on your environment)
3) If you can detect strong neighbouring wifi, use a channel 5 stops away from strongest.
4) Relocate cordless phone base or video sender etc.
5) Be prepared to move the computer (or at least turn it so your body is not between the router signal and the wireless adapter's antenna.