Just to be clear, this is an independent user forum. Casio is not able to respond to service requests here. They have a service contact page as posted above. Each region of the world has their own unique contact page. You'll need to search the web for Casio support in your region.
Casio support covers these under warranty for a period of time. This is done by contacting your original Casio dealer first, and then Casio support if the dealer is not able to assist. After warranty has expired, any qualified service tech can offer assistance and repairs.
Unfortunately power issues are either a faulty power supply (the AC adapter or the outlet itself), or a fault in the instrument (buttons or circuits). It's difficult to help diagnose and repair these things through a user forum. If a DIY solution is desired, you'll need to know something about diagnostics and repairs.