If the system has not been operated in a few weeks or longer, the degasser channel may be clogged by crystallization caused as the mobile phase present in the degasser evaporated. You will need to wash it out with DI water. The degasser does NOT tolerate high pressure. Please do not force water into the degasser using a syringe or anything else. Position a bottle containing HPLC grade water at a level above the degasser inlet. Aspirate water into the tubing coming from the bottle to prime the system for a siphon effect and connect the tubing to the degasser inlet. Leave the degasser outlet open. The siphon effect will pull water into the degasser and dissolve the crystals inside of it. You may need to connect a syringe to the degasser outlet and aspirate gently to start the flow of water.  It may take several hours or even overnight for the salts to dissolve.  See picture below.