In my little trailer the pump is pretty loud, leaving no doubt as to whether or not it is running. It sounds like your pump is actually running.
If the pump runs and runs (without any faucets open), the first thing I’d be looking for is leaks. The next would be for air leaks into the piping or bad valve positions on the suction side of the pump. Maybe the folks who winterized it didn’t get the winterization valves aligned properly (or left it in winterization mode).
2021b Micro Minnie 2100BH
2017 Ford F-350 SRW diesel