Do you have to flip a lever to change from city water to tank fill when connecting the hose? Or, do you have a gravity fill for the tank and a female fitting for the city hose connection?
Also, you might try opening all faucets, turn on the pump, and when water comes out the faucet, turn them off. Upon turning off the last one, the pump should stop and the system will be pressurized. The pumps often won't draw water, gravity has to carry it to the pump and it might need the air to be released from the lines for the water to flow.
If the above doesn't do it, check that filters and screens aren't blocked and valves are all open.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI