I have a wild caught ARN, and she hardly ever makes any noise. I do love it when she does! But she's pretty quiet! She's been with me for several years. Actually, I've honestly never seen her drink.... Eating, yes, but not drinking! And I know she uses her water dish!
Your ringneck is still rather new and could still be settling in. I agree, give it time as long as your baby is healthy, there shouldn't be anything to worry about.
If your baby appears sick/lethargic, do take him or her to a vet!