Cannot determine wifi password for WN3000RP wifi extender. Its not the same as router.

Hi. Recently switched from sky broadband router to Vodafone router. Connected to existing Wi-Fi extender WN3000RP. Devices can connect to router using Wi-Fi password but devices cannot connect to Wi-Fi extender with the same password. Devices can recognise the Wi-Fi extender but the password is always rejected. I have no device that supports a direct LAN connection to the Wi-Fi extender. How do I discover the password for the Wi-Fi extender? Any help is greatly appreciated.