Please check the following steps to see if it helps:
 

<ul><li style="list-style-type: disc;">Please note that the solar panel will only function properly in direct sunlight and not through a window.</li></ul>
 

<ul><li style="list-style-type: disc;">Keep in mind that the output amperage of the solar panel is not consistent throughout the day and varies depending on the season.</li></ul>
 

<ul><li style="list-style-type: disc;">Please check the temperature as it can affect the performance of the solar panel. When the temperature is around 20℃, the intensity of sunlight may not be strong enough.</li></ul>
 

<ul><li style="list-style-type: disc;">Try using the solar panel with a different phone and cable to see if that helps.</li></ul>
 

If you have any questions, please contact <a href="https://support.anker.com/s/contact-us" style="text-decoration: none;" target="_blank">us</a> for further assistance.