Check at fitting where hose hooks to camper. Most have cone shaped screen with rubber seal. Could be jammed up or missing. Similar to yard hose but has screen
Most pedestal water hookups have a backflow valve on them. There's a pin that sticks out..... so if your hose or pressure regulator has a screen on it, it's stopping you from getting a good seal. I learned this the hard way. Again, pics would help.