First make sure the ssid is written the same on your router and the wii
First try without any encryption. Then if it works you can move up to bett encryption like WPA-PSK or WPA2-PSK with AES key.
Enter the MAC of your Wii in te router also (best is always make a whitelist of the computers you want to connet using the MAC addresses).
If you have put a password be sure they are written the same way.
If you can´t get conection, try putting the router and the wii in the same room.
Try conecting on channel 1 or 11.