Suggest to watch tutorial video to top up washer fluid. Suggest to diagnose at workshop if problem cannot be solved. The usual procedure and keypoints of diagnose are:
1.Check the reservoir tank and supply hose, replace if necessary.
2. Use the scan tool to diagnose the sensor, replace if it is faulty.
3. Check the reservoir box and supply hose, replace if necessary.
4. Tes the replacement part after repairing done, return the car after confirmed the problem has been resolved.