Doorbell 3 Solar Charger not holding charge

There has to be a problem with doorbell 3 and its battery and solar charger. battery lasts 3 days with or with out solar charger. I have been told its too far away from the modem/router. Its six feet and only through glass. It just doesn't work. We use two batteries and switch them back and forth so we never go with out power. Such an inconvenience.