My unit will not build up pressure pass 30 psi

You can use a solution of water and a little dish soap, pour it around the hose mounts while the unit is running to see where you are losing pressure due to a leak. That will let you know what needs to be repaired or possibly replaced.

It might be a leak if the unit keeps running when it gets to 30PSI on the tank gauge. If the unit stops at 30PSI on the tank gauge then the pressure switch is faulty. If it goes to normal max pressure on the tank gauge but is only 30PSI on the regulated gauge, then it is either a manifold or a cockpit problem. The knob will adjust that pressure to something equal to or lower than the tank pressure. Either it needs to be adjusted to your desired PSI or needs service. Click on the picture of the unit and go to the manifold page to see how to clean/fix that adj knob.