The
check valve is 16psi, The pump has a reverse
check valve which is well over 100psi.
Have you primed the pump with the hose in place and had fluid come out?
Then reconnected the hose to the nozzle holder and test sprayed yet.
Also be sure you look at the arrow on the top of the pump and make sure you have it going the right way and you don't have the inlet on the outlet side.