Your symptoms point to a salt bridge in the tank. If the softener is going into the recharge cycle properly then a salt bridge will prevent the water that enters the tank from mixing with salt to make a brine solution that will clean the hard salt off of the resin beads. I provided a page from your owner's manual that describes this condition in the image below. Follow the steps below to check the tank for this type of salt bridge.
If you do not have a salt bridge, then a failure in the control or the valve assembly could be causing this problem. The owner's manual provides diagnostics and troubleshooting for this type of problem. Here is a link for the owner's manual for your water softener:
Depending on the hardness of your water, the resin bed will normally be depleted in about 12 to 15 years. If your softener is older than 12 years, you may begin to see a drop in softening efficiency as the resin begins to wear out. This would not cause a decrease in the use of salt but it can affect softening performance.