Hi, welcome to GoY, unfortunately when solar cells fail, there's nothing you can do, except buy a new one, Derek.

May sound obvious but double check that the cables are plugged in and not damaged and that the panel is actually pointing towards some sunlight and isn't overshadowed.

My mother had one of these it was fine one year - next year nothing, simply because a tree had grown up over the spring/early summer when she wasn't sitting outside to notice.

Perhaps you should check the battery
I presume they are like solar lights which have a rechargeable battery