I've configured the line keys on the SPA509G and SPA525G as follow:
Disabled
Private
fnc=blf+sd+cp;sub=2002@$PROXY;nme=Surat
After that, the BLF and SD function are working as expected but the CP function is not working. When a line key on the configured phone is blinking red and I press it the phone answers "Unavailable To *36". *36 is what I configured in 'Attendant Console Call Pickup Code:' in the Attendant Console Tab.
Best regards,
Michael