You can try any or all of these steps to help with this problem:
1) Check that the password being entered is correct.
2) Check that 802.11b is enabled on the access point or router.
3) Ensure MAC filtering is not switched on in the access point or router. If it is switched on, only known devices will be able to connect to your router.
4) Check that your network has an internet connection.
5) Check that the sensor is in range of the router.
6) Check to see if the router has the latest firmware.
7) If the access point or router has WEP Encryption ensure that the HEX key is being entered rather than the password. You can find the HEX key in the internal settings of your access point or router. Alternatively, search the web for resources to help convert your password to a HEX key.
8) Check that DHCP service is running. This allows the sensor device to be allocated an IP Address. Normally, the DHCP service runs in either your router or on a network server. Make sure that the configured DHCP IP address range allows the addition of new devices if not, then extend the range.
9) If your wireless network uses WPA Enterprise, make sure that the correct authentication type is selected from the drop-down box. Only the types listed are supported.
10) If your access point or router has a wireless mode setting, this must be set to ‘Mixed’, not ‘Greenfield’.
11) Make sure that the SSID name does not contain spaces.