My pump pressure jumped up suddenly and my flow stopped. What’s wrong with my system?

Typically in this situation, something has seriously and completely blocked the flow path, such that no matter what effort the pump goes to in order to push the necessary mobile phase through, it cannot be achieved. This can be in the form of a serious filter or frit blockage (often due to a precipitation effect of some sort), or it can be due to a large contaminant blocking the tubing through hole. Another source of this problem could be the outlet check valve malfunctioning, not allowing fluid to pass in the appropriate direction. The best way to solve that problem is to start at the furthest point along your flow path where the blockage could theoretically be, and begin disconnecting junctions along the path, all the while monitoring the pressure to see when it drops. As soon as you release a connection in front of the blockage, you should see an almost instantaneous release of pressure, as well as the return of fluid flow.