Ring spotlight cam won’t work

I have fully charged the battery that went dead in the unit. The unit will not turn on again and the light does not flash. Our other battery (fully charged from another spotlight cam) does power our other unit but will not power this unit. The dead battery (now charged) will not power our working unit. I have tried the 20 second reset method and followed all instructions through the app and other Ring approved forums. Any advice?? Thanks