I presume you have a Fluid-o-tech vibe pump in the BZ35e. If so then it is exactly like mine. Low pump pressure could be a result of the diode in the plug connected to the pump being blown (this happened on mine, but didnt result in low brew pressure). Otherwise, can you hear the pump operating? If not, then you problem might be with the relay (simple and cheap to replace). Before that in the chain is the brain box, then the switch panel itself. Its hard to diagnose without seeing the machine and putting a multimeter across it. If the pump is trying to run, then the brain-box/switch panel should be fine. The OPV setting might also be incorrect, of the OPV not functioning properly. This is a simple mechanism consisting of a slotted screw (white plastic adjustment), spring, ball and seat. If the ball isnt seating properly, then the OPV will be stuck on and bypass the pump giving you line pressure only.
There are plenty of options to explore. You have to try and systematically reduce these.
Feel free to ask more questions if you have some specifics.