2. Remove the end of the tubing shown here. You may need a second wrench on the solenoid nut to hold it in place while you unthread the 14mm nut. Once unthreaded, it can be a bit tough to get the tubing end out of the fitting, but it will come out with a tug.
3. Clear out the end of the tubing with a pick or something else that will fit inside. It should be free of any scale buildup.
4. Reinstall tubing end into the fitting. This can be a bit tough but it will eventually fit back into place with some physical encouragement.