[Check 1] Have you put the water in the right place?
Please put the water in the water tank with the grey part in the middle (the heater).
[Check 2] Did you put enough water in the water tank?
If there is not enough water in the water tank, it won't be able to create steam. Even if just cooking for a short time, you should ensure that the water reaches at least the top of the heater (the grey part). Even if you have put in enough water, it will take some time before it starts steaming.
[Check 3] Is the heater (grey part) dirty?
If there are minerals from the water adhered to the heater, it may not transmit heat correctly and steam may not be created. If there are changes such as discolouration of the heater - brown, black or white - or peeling of the surface, care of the heater will be necessary. Please carry out a descaling.