This solution also shows and includes the Power ON OFF key line paths.
There are two Keypad ESD-EMI filter is being used in the circuit. The keypad line paths used nine input and output filtering lines in the Filter IC while the power ON OFF key also shared in this filter IC.
Nokia 5220 keypad Not working solution
If trying to replace the keypad filter IC you may also trace and check first each of its corresponding connection line paths, while the Filter IC being removed and just inplaced a new one after ensuring that all the line paths is okay.