7 of 20 Lights offline

I have had my lights for over a year and until recently have work fairly well. I have had to bring them all in to charge on occasion (low sunlight or constant movement wearing down batteries). I have 7 out of my 20 lights that show offline. I brought those 7 in to charge. As soon as I plugged them in they flashed and blinked for a minute or two then steady dim light meaning charged (also showed 100%). All of these lights showed online now. After I unplugged them and took them back out to their outdoor home they showed offline. 4 of the lights are within 10 feet of the bridge and right next to other lights that are connected. 1. How do I get them to reconnect and stay connected2. How do I do a factory reset of the lights and connect them like it is the first time again. Hoping this will work for me. I don't want to buy any new lights if they only last just over a year for me.