RANGE EXTENDER WN3000RP

3. The Extender’s wireless network name (SSID) changes to your
existing Wi-Fi network name, with _EXT at the end of the name.
For example:
Existing Wi-Fi network name: MyNetworkName
New Extender network name: MyNetworkName_EXT
4. To connect additional Wi-Fi devices to your Extender network, use
the same network security key (passphrase) as is set on your
existing wireless network/wireless router

I did all the step correctly, but when i try to insert the psswrd, is always saying is incorrect. but ovviously im sure the psswrd is correct.. what can be the problem??