Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Have you tried a reset of the Yamaha instrument in question? I would advise it... it might just get it working again.
From an Off status, hold down the highest white key on the keyboard, while turning On the keyboard with the power switch, keep holding down the white key for at least 5 seconds.
There is a more severe reset to try, which is similar, but you hold down the highest white key, and also the three highest black keys, while turning On the keyboard.
Does this produce any result? if not your Yamaha keyboard is, unfortunately, in a bad way and will need repairs.
If you can tell me two things, if things reach this point, I can help you further though:
1. where (roughly) are you located, in Australia, please?
and 2. is the keyboard in question less than a year old?