Hi and welcome to Just answer.
If your machine is Saeco Incanto Deluxe S-Class. Please try this,
Fill the water tank with warm water. Turn on the machine and dispense hot water (your model may require to press the hot water button first or just open the steam wand). Continue to dispense hot water till the ventilate message disappears which could take upto a cup of hot water.
If still, try to open the steam knob to dispense hot water and while it's dispensing push in the knob. If this doesn't help then most likely your steam valve is worn and is introducing air into the system or scale deposits are plugging up your flow meter. In either case the repair isn't easy but is affordable so I'd suggest taking it to your local Phillips Saeco repair facility.
Hope this information will be helpful.
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