check your pressure regulator - very often the cause of problems and hardly ever talked about
if you have the 400 psi pump you should have a big brass regulator you use to adjust the pressure - it should be greased on a regular basis otherwise the valve sticks and you get too much pressure building up in the pump and not coming out of the hose connector
5 min job, fully unwind the brass regulator so it comes off, there will be a big spring behind it, take that out, use some small nose pliers then to take off a solid washer and then the shaft, it will probably look corroded/rusted. Clean it, lubricate it with some good grease and reassemble. Should be done every 6 weeks or so and can save loads of trouble