Solar panel not holding charge

We have a new Netvue lite. It has been up for 10 days with the solar panel. The battery was at about 10% today. We have now plugged it in to charge. We have had only cloudy days since we installed it. Would over 100 squirrel visits a day affect it? They, of course, love the hot bird seed! Also, where is the waterproof cap. Thanks so much for your help.