I think you are pushing the beer too hard for your beer lines. You might have a really well carbonated (if not overly carbonated) beer but you are losing all of it in the pour. Try relieving the pressure, dialing it down to 8 psi or so, and if the beer won't come out, slowly increment up until you get beer, but not a lot of head. Unless you have beer lines a quarter mile long, 40 psi is way too high to try to serve. Hope that helps.