Solar lights use a small photovoltaic panel. When the sun shines on them, electricity is generated, storing power in a small battery bank. When a solar lights fails to light up, there are a couple of reasons for this. It only takes a few minutes to get your lights up and running again.
Remove the glass. You may need to unscrew the glass to remove it.
Remove the battery cover, if there is one. You may need to unscrew this.
Clean the battery ends and terminals. You can remove any rust or corrosion with sandpaper. Remove any bugs and dirt.
Test the batteries with a battery tester or a volt meter on a low DC setting. If the batteries are fine, it is probably a faulty photocell. The photocell is a light sensor that controls when the solar lights turn on or off.