Check the power source. Make sure that the piano is plugged into a working outlet and that the power switch is turned on. If the piano is plugged into a power strip, try plugging it directly into the outlet.
Check the power cord. Make sure that the power cord is securely plugged into the piano and the outlet. If the power cord is damaged, replace it with a new one.
Check the fuse. The piano may have a fuse that has blown. If the fuse is blown, replace it with a new fuse of the same type and amperage.
Check the power supply. The piano may have a power supply that has failed. If the power supply is failed, replace it with a new power supply.
Check the internal connections. If the piano has been moved recently, it is possible that the internal connections have come loose. Open the piano and check the connections between the power supply, the power switch, and the circuit board. Make sure that the connections are tight and secure.
If the piano still does not turn on after trying all of these steps, it is likely that there is a more serious problem with the piano. You should take the piano to a qualified piano technician for repair.