If the pump pressure reading is zero or nearly zero, there is a possibility that the tubing or degasser located upstream of the HPLC pump has been clogged. Please try to connect a disposable syringe to the degasser outlet using a degasser syringe adapter and aspirate with DI water. If water is coming into the syringe, please check the flow of the pump.  If there is no/little flow from the degasser, please see our article on how to handle a clogged degasser.