If the "Keypad Locked" screen displays when you press a key, unlock the keypad.
Try changing to another program.
Try pressing different keys.
Check if you are properly pressing the key. You should fell a "click" when the keys are pressed.
Using the tip of a pen, press the hard reset button on the back of your remote assistant. Please note that in this case you have to repeat the pairing between the Remote Assistant and the Sound Processor.