Hi @edhasaquestion ,
You'll need to first carefully open the toy to access the control board and any switches etc.
Using either an Ohmmeter or a Voltmeter start checking that the power supply circuit from the batteries is getting to the board via any On/Off switches etc.
(Ohmmeter for point to point testing with the power removed. Voltmeter if you wish to test with the power connected).
If the power supply circuit appears to be OK then, since there is no schematic diagram available online that I can find, you'll either have to chase power through the board / switches etc using the Voltmeter or use the Ohmmeter to do point to point testing with the power removed, to find out what is going on.
Also look for any obvious problems such as broken wires, dry solder joints, dirty switch contacts, cracked components etc.
Welcome to the wonderful world of fault finding in electronic circuits without the aid of a wiring diagram or service manual ;-)