Due to insufficient cold water pressure, the normal water supply was disrupted. This issue is common during peak water usage periods when a high number of people are using water. Low water pressure prevents the solar water heater from refilling. This problem can be resolved by adjusting the refilling time to the middle of the night or early morning when fewer people are using water.

2. The Shangshui solenoid valve encountered a malfunction. Due to the relatively dirty water quality and high amount of impurities, the filter screen often gets clogged, preventing normal water supply. This issue can be resolved by cleaning or replacing the solenoid valve.

3. A fault in the water temperature and level sensor has prevented it from properly detecting the water tank level. As a result, the function to fill water at the set level is not operational. Simply replacing the water level sensor with a new one should resolve the issue.

4. Solar water heater glass vacuum tubes may crack or leak due to aging outdoor water pipes after years of use. Severe leakage can also prevent the solar water heater from refilling, as water will completely drain from the damaged area. Simply repairing the leak as soon as it's detected should suffice.

5. If there's air trapped in the solar water heater's piping, it can prevent water from flowing. Airlock can also prevent the solar water heater from dispensing hot water. It's necessary to promptly remove the air from the pipes.

6. A common yet often overlooked cause is foreign objects blocking the pipes. This situation is not easily detected, so patience is key when inspecting the pipes section by section. Simply remove the foreign objects to resolve the issue.