If your system is not refilling the brine tank on the brine fill cycle, first check what the fill time is set to in setting 8. Our default is 012 minutes and the brine fill should not be lower than this.
Check the brine line connection at both connection points, one at the top of the control head and one at the float valve assembly.
Disconnect each connection point, apply silicone grease or any food-grade oil to the ends of the line and reinstall into the connection points.
Check for water filling back into the brine tank.
If no water is filling in the brine tank, disconnect the brine line from the float valve assembly to test for a brine fill separate from this connection.