Solar Panel not charging cam?

At what point should the solar panel kick in and start topping up the battery? Have a stick up cam (3rd Gen) and the app shows the solar panel is connected but not charging. Solar Panel was connected when battery was at 85% and now a few weeks later the battery is 30% and solar panel has never charged the cam. Been in plenty of direct sunlight in that time. Confused if the panel is actually ever going to work properly?