Where are you in the world?
If you are in upper North America then guess what? It is winter and the sun is weak because it is low in the sky. Today was sunny and tonight my solar garden lights were normal for about half an hour after charging all day. In summer they light all night long. I am in Canada but very close to the USA border.
A window's glass reduces the sun's intensity to half or less. The solar panel must point directly at the sun, not straight up and not to one side.