All of the water that enters this washer passes through the solenoid valve assembly that is attached to the rear of the dispenser cavity (see first image). The water entering this assembly has four exit paths. Two paths allow the water to go through the detergent cavity and the bypass to provide the normal fill water for the washer. The other two paths are controlled by the timer. They direct water through the bleach cavity and the fabric softener cavity for proper dispensing of these liquids. Understanding the operation of the dispenser is a key to diagnosing your problem.
It appears that you may have a failure in the dispenser solenoid valve that directs water through the fabric softener cavity. The timer will close a contact to energize this solenoid valve during the final fill of the rinse cycle.
To diagnose this failure, the technician would first unplug the washer and then check the wiring connections between the timer and this fabric softener solenoid valve. If wiring appears okay, the technician would reconnect electrical power and set the timer to the portion of the cycle that initiates the final rinse fill. A voltage check would be taken to determine whether the contact in the timer is closing properly to energize the fabric softener solenoid valve. If not, then the timer would need to be replaced to fix this problem. If the timer contact is closing properly to apply proper voltage to the solenoid valve, then the valve would need to be replaced. I do not recommend conducting this live voltage test yourself. This type of check is dangerous. If you are able to unplug the washer, access the valve and check the wiring, I recommend taking this step first. If the wiring looks okay, then you could remove the wires from the two solenoid valves and check the resistance across the leads of each valve (with the washer still unplugged). If the resistance does not match, then this would verify that you have a bad valve and the assembly would need to be replaced. NOTE: Even if the resistances are identical, you could also have a clogged or defective valve that is not opening or allowing water to pass through. The valve would also have to be replaced in this situation.
The procedure for replacing the dispenser solenoid valve assembly is illustrated in the second image below. To remove the top panel of this washer, you will need to unplug the washer and remove screws on the back side of the panel and then release the front of the panel from clips on the front console.
If you have more questions about this problem, resubmit your question with additional details.