multi possibiliites.
air in the water house feeding pressure washer. it can take time for the air to move out.
you say pressure but how much pressure? if you are on a well. then good chance you may not have enough pressure. well's for regular homes tend to be set at a lower pressure rating. vs folks in cities were pressure can be much much higher.
pressure is only one factor. gallons per hour. or rather flow rate. you might have 60PSI at the garden house feeding pressure washer. but if there is a kink in garden hose. or using cheap smaller size garden hose, and have a old home with metal pipes that have corrosion build up. you may only be getting a trickle of water, vs say 2.5gph to 20 gallons per hour. or more.
garden hoses come in different inside diameters. the larger the diameter the more likely better off you will be.
you might have some sort of screen on the inlet side of pressure washer were garden hose hooks up that might be plugged solid with stuff.
