No water flow when dry camping

Thanks for the imput I will check the valves. The water tank was full it is under the bed right next to the water pump so I could see it full as I changed the pump. I had both valves open the one that says "fill" and the one that says "use". Should I have closed one to use the onboard pump? I tried closing and opening the valves when camping and it made no difference in water flow. Also I made sure all the winterizing valves were closed. I had a toyhauler trailer before I sold to buy this motorhome but it had a separate fill valve for city water and for filling the water tank so I am still learning how to work this thing.