The solar charger circuit has 3 LEDs (lights). Here are some of the combinations that you might see, and what they mean:
What does it mean if the top (red) and bottom (amber) LEDs are blinking rapidly?
These two LEDs will blink rapidly when the input power is unstable, e.g. you have a solar panel plugged in, but there isn't much sunlight. Once you move the solar panel(s) into better light (ideally direct sunlight), the blinking should go away and you should get solid bright lights.
What does it mean if all 3 lights are on?
It means the battery pack is either too hot or too cold (most likely the former). If it is warm, immediately unplug all solar panels and any other devices you have plugged in. If the battery pack is in the sun, move it into shade (the space behind the solar panel works). Once the battery pack has cooled, resume charging with one solar panel.
What does it mean when just the "Charging" light is on then fades?
It means the battery pack is almost completely drained. Charge it from a single solar panel (or the AC adapter) for at least 2 hours. If you have two solar panels, plug in the 2nd panel after waiting at least 20 minutes.