Hi,
What is the make and model of the router?
WPA stands for Wi-fi Protected Access. In a wireless network, the WPA key is a password that protects the network from outside intruders. If a wireless router is set up with WPA encryption, you need the WPA key for network access and to make changes to the settings of your network.
I would suggest you refer the link and check if it helps.
I would also suggest you contact HP for support.
http://h30434.www3.hp.com/t5/Printer-networking-and-wireless/bd-p/Networking
I would also suggest you contact the manufacturer of Router for WPA key.