A different possibility, but experienced by several A-framers. Regardless of whether pump is left on or off, especially while trailering, pump gets locked up by pressure build-up from heat, etc. Or can be vapor lock. The very small amount of plumbing doesn't allow for any thermal expansion. So turning on the pump does nothing but run the motor. All the pressure has to be dumped before the pump will pump again.
I have gotten in the habit of dumping water pressure when getting ready to trailer. I turn off the pump and open the outside shower valves (both hot and cold), and let the water flow until it stops from lack of pressure. I then close the outside shower valves. Now, pump always works properly when we set up at next campsite or home.
2019 Flagstaff T21TBHW A-frame