1. Loss washer fluid can be top up.
2. Leakage on the hose causing loss of washer fluid. Check the hose and connecting parts if there is leakage.
3. Washer fluid quality do not meet standard requirement, affecting the measuring function of the sensor. Suggest to replace washer fluid with better quality one.
Suggest to watch the tutorial video. Refill the washer fluid according to the video guidance.