I attached the hose to the fill spot on the driver's side, went to the panel on the passenger side and moved the valves to fill the tank, turned on the water and it won't fill the tank. I even had a mobile RV repairman here to confirm I was doing it right and he said I was. I then called the previous owner (we just bought it) and he said that's the way to do it and they've never had a problem. Help!