crwdns2893792:0crwdne2893792:0 Henry H ,
Hi Ken, is your steam wand or anything else leaking when trying to pull a shot? If so you'll need to resolve that before the group head will get the full pressure from the pump. If nothing is leaking then I would check to make sure your portafilter basket and group head screen aren't clogged, and perhaps try a slightly coarser grind on your coffee as well. You'll want to avoid using vinegar in the machine as it can reduce the life of the pump; use a commercial espresso machine descaler like Dezcal or Durgol instead.