Open the hot water and steam knobs and leave running for a minute or so.
You should have better steam and flow from the hot water wand by at least a minute in and then should be good to go. If you still don't have flow after this time then further diagnosis will be needed.
It's common symptom on these machines when they sit unused without water in them for a while, the pumps drain out and air gets into the lines. Opening both knobs allows water to flow through the whole system and expel any air.