Presumably you mean that after playing the keys the sound stops. Is this correct?
What do you do to make it play again?
There may be a loose cable connection between the keyboard circuits and the mainboard and the vibrations caused by playing may cause it to disconnect.
Alternatively, is the power disconnecting from the keyboard (no lights etc) when you do this?
In any event the keyboard will have to be opened and the problem investigated.
Here is a link to the service manual for your keyboard player. It details the steps to dismantle the keyboard and has all the relevant information you need to diagnose the problem
To download the manual when the sentence below the Document preview box changes from This file is downloadable free of charge: ...processing... to This file is downloadable free of charge: Get Manual, click on the Get Manual as this is the download link. Be patient, it takes a little while to find the file.
Hopefully this is of some help.