When you buy solar powered lights, they are actually kept alive by the sun charging the batteries inside.
These are generally AA batteries of the rechargeable type. If your solar lights all of a sudden stop working, it just means that the sun has not been strong enough to maintain the charge of these batteries!
Do not throw out your lights!! Buy yourself a cheap AA battery charger, put your batteries in it over night and put back into your solar powered device....viola!
Your solar lights come back to life and you have a beautiful garden feature once again!