How are you doing there? If you haven't got supply pressure through any of the plumbing, I'd start at the source end and work from there, forwards. Your supply hose from the house is in this path, also.
There have been a few posts about supply pressure/flow from folks with new trailers. It can usually be due to debris from the factory assembly process or a failed/pinched supply line. The failure of the inlet check valve is also possible. They use the cheapest stuff imaginable on some models of trailers.
Good luck!