Second battery not charging

My system has been active for over a year, no issues until now. I noticed yesterday that my secondary battery was at 0% with a red light and flashing single green. I have tried fully charging/discharging but only the primary battery charges, also updated firmware. Any ideas?

Call GE support!

The battery will need to be charged independently from the system before it will hopefully recover. Call your installer or get GE to come out and sort it.