I have a Bosch sennsixx B25L with steam problem?

When using the iron it heats up the plate and water fine. As soon as it is used the steam comes out fine. The iron then cools and stops steaming. If you switch the iron off and on again it starts to work again. I have washed the limescale from the tank. I am thinking of using a descaller (although it says not too) as the iron is useless as it is