They can if THEY want to. If nothing has changed, there would be no reason for the parrot to do something new.
My little Meyer's parrot
learned to "talk" in stages. I taught her to whistle "Charge" and every time she did, everyone in earshot would shout "Charge". She now croaks something that sounds like the word.
Lately (about six months later) she has been saying-not croaking, saying, "Hello" when I get her out of her cage.
Sunnies in general are considered better talkers than Meyer's in general, but some African Grays and Amazons (best talkers in general) live long lives without ever saying a word. It depends on the bird and the circumstances.