Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do what I can to provide the right answer to your question.
First: it obviously has no sound because of a keyboard chip, or breakage, obviously.
Second: open it and examine the keyboard chips area - probably not requiring that you remove any keys, but I'm not sure I know all the details of this model.
(Ideas: it isn't the audio amplifier stuff that's down, but rather the keyboard in some fashion. Or perhaps, the tone generation.)
I think you might be happier with another Expert's approach to this question, so I have Opted Out, opening the case to other Experts with more specific knowledge of Ensoniq keyboards.
(I have no power myself, over refunds. For all issues of billing, payment, subscription terms and status, etc., I must refer you to Customer Support at JustAnswer.com, which may be contacted through:
They will no doubt address your concern, if you contact them, with reasonable promptness.)