This usually means the valve or its timer rather than the resin, and the house is on hard water while it is stuck.

The control valve steps through fill, brine draw, backwash and rinse on a motor and a cam. If a piston, a switch, or the board stalls partway, the valve parks in one position and keeps sending water to drain.

Look for a drain line that runs for hours, a brine tank that keeps filling or never empties, soft water that disappeared overnight, and a water bill that jumped without anything changing in the house.

Do not buy salt or resin for this. Neither one moves a stalled valve, and running it stuck wastes water the whole time. Put the unit on bypass until someone looks at it.