[JRTJH]

It sounds like the pump "inlet" is not drawing water from the fresh water tank. Depending on how your trailer is plumbed, you may have a valve that is turned to draw antifreeze into the pump and that valve needs to be turned "back to the other position" to draw water from the FW tank. Or, you may have a separate fitting with a hose on it that you must install on the pump inlet to draw antifreeze and then reinstall the FW tank hose/fitting to draw from the tank. If that fitting is damaged or the O-ring is not sealing properly, air will be drawn into the pump and it can't create a vacuum to pull water from the tank.

So, check your valves if you have a "water system center" and check your fittings on the inlet side of the water pump if you have a "old fashioned" system.