Every device which connects to a wireless network has a wireless adaptor, either inside it, or attached to it on some way. And every wireless adaptor has a unique number. In addition to the "standard" wireless security involving a password or passphrase, wireless networks can be configured to allow connections only from those devices whose unique number it recognises.
If this is how your wireless network has been configured, then you won't be able to connect any new devices until either you disable this additional validation (not recommended), or add the new device to the list of addresses that the wireless router recognises.